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Recent interest has uncovered the importance of understanding meniscal root anatomy, its effect on biomechanics of the knee joint, and appropriate treatment modalities. Meniscal root tears may account for up to one-fifth of all meniscal tears and have downstream consequences that can be as severe as total meniscectomy due to the unique force-dispersing properties of the meniscus. Meniscal biomechanics rely heavily upon the integrity of root attachments, and this historically overlooked etiology of knee pain and early onset osteoarthritis plays a vital role in maintaining the longevity of the knee joint. As meniscal root pathology becomes more commonly known and clinically assessed, an understanding of classifications, repair methods, and indications is important for surgeons.
Historically overlooked as an etiology of knee pain and early onset osteoarthritis (OA), the meniscal root plays a vital role in maintaining the longevity of the knee joint.
Reported to affect nearly 100,000 patients annually, meniscal root tears (MRTs) account for up to 10% to 21% of all meniscal tears and have been labeled as a “silent epidemic” due to their widespread underdiagnosis and the rapid progression of untreated injuries to OA.
Altered tibiofemoral contact mechanics due to lateral meniscus posterior horn root avulsions and radial tears can be restored with in situ pull-out suture repairs.
Demographic differences have been reported for types of MRTs, with young male patients more likely to present with lateral MRTs, often in the setting of multiple ligament knee injuries, knee trauma, or concomitant anterior cruciate ligament (ACL) tears.
Medial MRTs often occur via a low-energy mechanism and are more common in older patients with higher body mass index (BMI) and existing degenerative changes in the knee.
An MRT is defined as a complete bony or soft tissue avulsion of the root attachment or a radial tear that occurs within 1 cm of the meniscal root attachment.
Altered tibiofemoral contact mechanics due to lateral meniscus posterior horn root avulsions and radial tears can be restored with in situ pull-out suture repairs.
Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site: in situ pull-out repair restores derangement of joint mechanics.
A root avulsion alters the tibiofemoral load distribution across the tibial plateau because of meniscal extrusion, which increases the pressure on the articular cartilage. Past biomechanical studies have demonstrated changes in area and contact pressures across the tibiofemoral joint following an MRT are comparable with a meniscal deficient state.
and MRTs often occur in the fourth or fifth decade of life. Early detection is crucial to restore native knee joint loading and for the prevention of articular cartilage degeneration.
For decades, meniscectomy was the standard treatment following meniscal injury, and continues to be widely utilized. However, given the significant risk of progression to OA, treatment by meniscectomy has come under scrutiny and current research emphasizes meniscus preservation with anatomically oriented meniscal root repair techniques.
Clinical and radiological outcomes of meniscal repair versus partial meniscectomy for medial meniscus root tears: a systematic review and meta-analysis.
This article will review the anatomy and biomechanics of the meniscus root attachments, with diagnostic and surgical treatment pearls, and discuss the current state of MRT repairs and salvage techniques.
Anatomy/biomechanics
Meniscus anatomy: Structure is function
The medial and lateral menisci form 2 C-shaped borders filling the triangular space between the tibial and femoral articular cartilage surfaces and the joint capsule. The meniscus itself is roughly the shape of a collapsed triangle on cross section, with a broad, vascular outside body which thins to a less vascular and then ultimately avascular apical ridge between chondral surfaces. This unique space-filling shape leads to increased joint-surface contact area.
The lateral meniscus is smaller and more circular with its anterior and posterior roots nearly meeting at the lateral intercondylar eminence. Both anterior and posterior medial meniscal roots lie peripheral to the lateral root insertions, forming more of a horseshoe or C shape.
The medial meniscus, perhaps due to the greater percentage of weightbearing through the medial femoral and tibial pillars, is more rigidly attached to the tibia and the surrounding capsule, and therefore, less mobile. The medial meniscus therefore provides a certain measure of stability for the femoral condyle on the tibia—a sort of shallow, rounded cup holder. The lateral meniscus in comparison has more laxity allowing a small amount of anteroposterior glide along the tibial surface so as to better move with the lateral femoral condyle during natural axial rotation about the tibiofemoral joint. Much of the posterior horn of the lateral meniscus lacks meniscocapsular attachments, thereby allowing this increased mobility. However, the meniscofemoral ligaments, which course from the medial most extent of the posterior horn to their attachment sites in the femoral notch both anterior and posterior to the bundles of the Posterior cruciate ligament (PCL), both confer notable stability namely to internal rotation and anterior translational forces.
While the meniscocapsular attachments and meniscofemoral ligaments are both important for meniscal stability, the most biomechanically important connections are the meniscal root attachments.
Furthermore, meniscal root integrity is crucial to meniscal function as a whole, because the disruption of these anchoring sites releases the circular tension holding the meniscus between the tibiofemoral cartilages.
The resulting axial compression through the tibiofemoral joint then pushes the meniscus out of the articular joint space, thereby diminishing the ability of the meniscus to adequately disperse axial tibiofemoral joint forces.
Biomechanics, stability, and sequalae
Foundational studies examining the biomechanical and structural characteristics of the menisci have established their critical role in modulating force transmission across the tibiofemoral articulation.
Furthermore, by increasing the contact surface area of the tibiofemoral articulation, the menisci function to spread compressive loads over a larger surface area, thereby avoiding the phenomenon of “point loading.” This dispersion of axial compressive loads across the knee helps to provide long-term protective effects to chondral surfaces and prevent progression of osteoarthritic changes.
In addition, the loss of stability caused by root tears leads to increased instability and motion across the tibiofemoral articulation, which puts increased strain on stabilizing ligaments such as the ACL.
It may also be that increased motion due to instability inferred by meniscal root pathology changes the biomechanics of the tibiofemoral joint to an extent that expedites the joint degradation sustained.
Pathology discussing diagnosis
LaPrade classification of meniscal root tears
The term MRT is used to describe damage occurring to one of the meniscal attachment sites within 1 cm from the meniscal root insertion.
Meniscal root tears can manifest in a variety of ways, necessitating the use of an appropriate classification system. The LaPrade classification for MRTs classifies MRTs based on the location and quality of the tear.
Unlike other proposed systems for classifying MRTs, the LaPrade classification for MRTs applies to both the anterior and posterior roots and separates tears into 5 types (Fig. 1).
Type 2 describes a complete radial tear of the meniscal root and contains 3 subtypes which differ based on their location along the meniscal root relative to the center of the root insertion; Type 2A occurs at less than 3 mm from the center of the root attachment, Type 2B occurs from 3 to 6 mm from the center of the root attachment site, Type 2C occurs from 6 to 9 mm from the center of the root attachment site.
Fig. 1Graphic displaying an example of each type of meniscal root tear as described by the LaPrade classification system. A Type 2A tear is depicted as an example for a Type 2 tear. Reproduced with permission from LaPrade et al.
Many studies have shown that the meniscus-deficient knee (eg, patients treated with meniscectomy or hemi-meniscectomy) almost always consistently and rapidly progresses to OA.
Furthermore, biomechanical models have shown the meniscal root-deficient knee to be biomechanically equivalent to the meniscectomized knee, and therefore, pose a similarly significant risk of progression to fulminant OA.
Studies have further demonstrated that nonanatomic repair of an MRT functions biomechanically similar to leaving the root left untreated and thereby would have significant long-term degenerative effects.
This is because the chondroprotective functions of the menisci are ultimately dependent upon their attachment to their respective anatomic root attachment sites.
Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site: in situ pull-out repair restores derangement of joint mechanics.
Point loading results in a phenomenon described previously as spontaneous osteonecrosis of the knee (SONK, now thought to be more appropriately referred to as “subchondral insufficiency fracture,” or SIFK), which is one of the identifiable signs of an MRT that can be found on magnetic resonance imaging (MRI).
Utilization of transtibial centralization suture best minimizes extrusion and restores tibiofemoral contact mechanics for anatomic medial meniscal root repairs in a cadaveric model.
Due to the acceleration of joint degeneration caused by MRTs, early diagnosis and prompt treatment is paramount for good outcomes. The clinical diagnosis begins with a detailed patient history and physical examination, and while certain radiographic findings may raise clinical suspicion, the gold standard for diagnosis is ultimately MRI and arthroscopy. Regarding the notoriety of MRTs as missed diagnoses, high clinical suspicion is required for the diagnosis, and clinician understanding of etiology and diagnostic signs is crucial.
History and physical examination
The difficulty of diagnosing MRTs stems in part from the lack of similarity to injury of the meniscal body. It has been reported, for example, that only 10% to 15% of patients with medial posterior root tears exhibit signs of knee locking or giving way.
When present, the mechanism of injury may lead to clinical suspicion of a root tear, such as a rotatory blow to a flexed knee which is assumed to be a common etiology. The presence of an ACL injury should also prompt examination for an MRT, most commonly in the lateral posterior root. Lateral meniscus root tears have been reported to have an incidence rate ranging from 2.65% to 16% in ACL injuries.
Epidemiology of combined injuries of the secondary stabilizers in ACL-deficient knees: medial meniscal ramp lesion, lateral meniscus root tear, and all tear: a prospective case series of 602 patients with ACL tears from the SANTI Study Group.
Physical examination is also limited in diagnostic utility, with some combination of pain with deep flexion (for posterior root tears), palpable meniscal extrusion, and a positive McMurray's test being present in only 50% to 60% of patients.
Physician gestalt after history and physical should direct further diagnostic imaging.
Imaging
Plain film radiographs including Rosenberg view are commonly obtained in orthopedic clinics; these images are less helpful for characterizing type of meniscal pathology and instead more helpful with inferring chronicity and severity of degenerative changes. Because root tears are structurally comparable to meniscal deficiency, the onset of rapid arthritic changes and increased Kellgren-Lawrence scores, particularly in young patients, should provoke investigation for MRTs. Long leg standing films should be acquired to assess coronal alignment as well. More recent literature has demonstrated that varus malalignment of >5° is associated with slightly decreased outcome scores compared with neutral alignment.
However, patients still have low failure rate and good improvements in outcome scores with varus alignment following meniscal root repair. Furthermore, concomitant osteotomy in this population was associated with significantly worse outcomes and therefore is no longer recommended in this patient cohort.
MRI is the most reliable noninvasive test for MRTs. Although in the past, studies had demonstrated specificity as low as 70%,
Signs of MRTs on MRI include increased signal resulting from fluid collection near the meniscal roots (Fig. 2), the ghost sign (sagittal cuts on which the meniscus is not identifiable in its normal position, Fig. 3), and coronal views showing meniscal extrusion greater than 3 mm from the tibial articular cartilage (Fig. 4).
Axial cuts can similarly be quite telling and representative of an MRT if the imaging cuts demonstrated have a good on-profile view of the root attachment (Fig. 5). Associated SONK, a misnomer more properly replaced with SIFK, is bony edema of the femoral condyles or tibial plateau thought to be caused by increased point-loading due to lack of meniscal support. This is another MRI finding that, in the absence of obvious causes, should prompt further investigation of an MRT.
Fig. 3Sagittal magnetic resonance imaging demonstrating the “ghost sign,” where the normal signal for the posterior meniscal root is absent (dotted outline).
Direct visualization under arthroscopy remains the gold standard for confirmation of MRTs, and due to increasing clinician awareness meniscal roots are commonly assessed with a probe on routine arthroscopy (Fig. 6). They may be visualized and assessed from standard medial and lateral portals, or for optimal visualization a surgeon may drive through the intercondylar notch or (less commonly) use additional posteromedial or posterolateral portals.
As awareness of MRTs and the biomechanical significance of MRT repair grows, nonoperative treatment has fallen out of favor excepting surgical contraindications. These include advanced arthritis (Outerbridge or Kellgren-Lawrence 3-4), high BMI, and coronal malalignment more than 3°.
For those patients who are not good surgical candidates or for whom meniscal root repair would offer little benefit, the mainstays of treatment are weight loss, activity modification, and bracing.
In particular, for patients with underlying varus alignment, the use of a medial unloader brace may prove very beneficial in reducing stresses upon the joint. Further symptomatic treatment with analgesics and ice may be recommended. For those with intractable pain failing nonoperative treatment, particularly in elderly patients, a total knee arthroplasty may be considered.
Meniscal root repair techniques
Numerous techniques exist to repair, augment, or reconstruct the meniscus, and there are many associated procedures that may aid in the long-term viability of the procedure, including repair or reconstruction of other stabilizing structures about the knee, or procedures aimed at ameliorating increased stress placed upon the meniscus. In last-resort cases, salvage procedures exist to offer the patient some form of relief. Meniscal root repair should be followed by a minimum of 6 weeks non-weightbearing with passive knee flexion to 90° only for 2 weeks to avoid overstressing the new construct.
Side-to-side repair
Perhaps the most obvious technique to restore meniscal function is an all-inside direct end-to-end repair of a radial tear. In the meniscal root, specifically, this would manifest as a gray area between type 2 C tears and very posterior radial tears of the meniscal horn. This is because a significant (∼10 mm or more) stump is required both for adequate tissue purchase, and because the device depth-limiter precludes use with anything less. This type of repair is more commonly used for lateral MRTs due to their propensity to tear incompletely with a flap that needs to be realigned. There are a number of ways to address these tears in a “side-to-side” fashion. All-inside with arthroscopic knot tying, all-inside with meniscocapsular fixation devices and inside-out techniques have all been described and can be utilized for these tear types. Furthermore, the described suture configurations themselves are highly variable. These configurations include: simple sutures across the tear, X type configurations, and rip-stop constructs combining horizontal mattress and vertical or simple suture patterns.
There are numerous things to consider regarding the ideal repair construct. The benefit of side-to-side repairs lies in their ability to incorporate existing meniscal tissue attached to the stump which provides an approximate restoration of native meniscal length and avoids the potential to shorten the meniscus (and thus overtighten it) which may occur with anchor or transosseous fixation. The size and quality of this stump is often less than ideal and therefore meniscal configurations that are the least damaging and help with load sharing are preferred. It is also important to consider needle size in the proposed construct because most all-inside devices are between 14 and 16 gauge compared with inside-out devices which are 23 to 25 gauge. This is a diameter difference of >0.6 mm which is substantial and can lead to further damage to an already compromised meniscal radial tear edge. Furthermore, risk of suture pull-through failure is not low and therefore a rip stop technique, which helps distribute the load to meniscal tissue across the suture material, could be beneficial. One additional factor to consider regarding technique is the potential risks of iatrogenic injury to the popliteal vessels posterior to the lateral root if care is not taken while placing sutures.
Suture anchors may be utilized for repair of MRTs at the site of root attachment, often utilizing additional far anteromedial and posteromedial portals to allow for more vertical orientation of anchors while maneuvering around the femoral condyles.
Arthroscopic transtibial pullout repair for posterior medial meniscus root tears: a systematic review of clinical, radiographic, and second-look arthroscopic results.
This technique uses 2 sutures per anchor to pull the root down to the anchor site, after which they are arthroscopically tied. A shaver may be used for bony bed preparation or shaving the underside of the meniscus to help with healing. Use of suture anchors may be considered in patients with a medial collateral ligament (MCL) tear which allows better access to the posteromedial root attachment, and also in patients undergoing concomitant procedures such as osteotomy in which there is concern for tunnel interference with the use of transtibial tunnels.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
Knotless suture anchors make use of additional portals as mentioned above for better access and orientation of anchor placement but use hardware designed to cinch the suture passed through the meniscus down to the anchor without need for tying knots arthroscopically, which reduces the technical challenge of using anchors for meniscus repair. The risks and benefits are similar to those stated for suture anchors in the previous section while adding the benefit of a knotless technique.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
Transosseous tunnel root repairs are commonly used and have been reported to be superior to other techniques in terms of anatomic restoration of joint kinematics including contact pressures and hoop stresses.
Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site: in situ pull-out repair restores derangement of joint mechanics.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
The essence of this procedure is 1 or 2 tunnels drilled from the anterior tibia and exiting through the anatomic root attachment site to which the root tear will be pulled with use of several sutures and ultimately fixed over the anterior tibial aperture through use of a cortical button, anchor device, or screw and washer fixation. The root attachment site is decorticated using a curette or a small socket to allow for a bleeding bony surface which facilitates bony healing into the root.
Single tunnels are less technically challenging, but it has been shown that the double-tunnel technique, which is the preferred technique of R.F.L., better approximates the root into an anatomic position due to the additional contact site which increases the dispersion area of suture tension on the root, and also allows for orientation of root fixation.
Many different suture configurations may be used to tie down the meniscal root, including a luggage loop, vertical or horizontal mattress (Fig. 7), or simple techniques. The preference of R.F.L. is for a vertical mattress suture which is relatively uncomplicated, reasonably quick to perform, and adequately disperses suture tension across the meniscus to avoid suture pull-through. The potential limitations of this procedure are the use of transtibial tunnels, which may cause concern for tunnel convergence or interference in a patient with need for multiple concomitant procedures; but this can often be overcome with careful planning (Fig. 8).
Fig. 7Medial meniscal root repaired with a side-to-side technique.
Fig. 8Normal position for a surgical button (white arrow) over the anterior transtibial tunnel aperture for root repair (left) compared with a modified transtibial position marked by the surgical button (white arrow) following proximal tibial osteotomy (right).
Despite repair of the meniscal root, it is common for meniscal extrusion to remain as identified on coronal MRI. It is assumed that the chronicity of meniscal extrusion due to undetected MRTs or delayed repair lead to scarring of the meniscal body to the capsule in an extruded position. A meniscocapsular release may be performed (alone, or in conjunction with stabilizing techniques described below) to provide mobility and anatomic restoration of the meniscal root to its attachment site.
Arthroscopic transtibial pullout repair for posterior medial meniscus root tears: a systematic review of clinical, radiographic, and second-look arthroscopic results.
Such procedures may also be performed without the use of a meniscocapsular release if the meniscal body is adequately mobile. This peripheral stabilization to centralize the meniscal body may also be achieved through use of a separate transtibial tunnel drilled laterally to pull the meniscal body down to bone similar to a transosseous pullout technique. The transtibial centralization suture has been reported to best minimize extrusion and restore tibiofemoral contact mechanics.
The use of biologics to stimulate meniscal growth and enhance meniscal healing has utilized a plethora of techniques with varying degrees of efficacy. Some ideas, such as injection of hyaluronic acid or various growth factors, have shown no ability to improve meniscal healing or have produced mixed results from varying authors. Other techniques, including the inhibition of known meniscal inflammatory factors such as matrix metalloproteases, were successful in stimulating meniscal healing but ultimately caused musculoskeletal toxicity and did not clinically improve patient arthritis. Yet other techniques show promise of improved meniscal healing in preclinical trials but have yet to be fully validated for clinical significance due to lack of high-quality evidence. These include use of platelet-rich plasma, fibrin clots, stem-cell therapy, and marrow venting (which originated when observation of meniscal healing after concomitant ACL repair was shown to improve meniscal healing rates).
Due to the detrimental effect of varus and valgus malalignment on meniscal root mechanics—including repair—osteotomy is sometimes used to improve outcomes for meniscal root repair. Indications for osteotomy should be dictated by degree of malalignment, patient age, and demand on the knee. Specifically, greater than 10° of varus malalignment is an indication for concurrent open-wedge high tibial osteotomy with MRT, while less than 5° indicates meniscal root repair only. The 5° to 10° range is a gray zone requiring attention to patient needs. Correction of valgus malalignment may be approached by use of a distal femoral osteotomy. Closing wedge osteotomy may also be used in cases where increased posterior tibial slope (also a risk factor for failure of meniscal repair) is being addressed. When proximal tibial osteotomy is used concurrently with transtibial pullout repair, it is recommended the root repair be performed first, and that the cut be outlined ahead of the root repair to be positioned slightly lower than normal to allow for increased amount of proximal tibia for tunnel placement.
Inclusion of osteotomy has been correlated with decreased patient-reported outcomes and will affect patient rehabilitation by increasing the non-weightbearing postoperative period by 2 weeks.
When concomitant cruciate or collateral ligament reconstruction is indicated, a good knowledge of anatomical and biomechanical relationships and the order of operative steps are critical to achieve the best outcomes. As described previously, there is a reciprocal relationship to biomechanical knee function between the stabilizing ligaments of the knee and the meniscus. In active patients with tears of both the meniscal root and one or more stabilizing ligaments, simultaneous repair and reconstruction is preferred. R.F.L. prefers an order of operative steps in which the meniscal root repair is addressed first up until sutures have been passed and anatomic restoration of the root has been visualized with manual tension on the sutures. Fixation of the construct is delayed until after the other procedures have been prepared and are ready for tensioning. This delay avoids stress to the new and somewhat fragile root repair during flexion of the knee, such as occurs when drilling or fixating the femoral ACL tunnel. Concurrent meniscal repair will also affect tunnel placement for tibial ACL and PCL tunnels. Recent work by Chahla et al demonstrated that risk of convergence between root tunnels and cruciate tunnels is notable, specifically between the lateral root tunnel and the ACL tibial tunnel.
Optimal tibial tunnel placement for medial and lateral meniscus root repair on the anteromedial tibia in the setting of anterior and posterior cruciate ligament reconstruction of the knee.
They assessed differing trajectories and found placement of root tunnels parallel in the sagittal plane to the ACL tunnel minimized convergence. Furthermore, care should be taken specifically in double-bundle PCL reconstruction techniques to ensure the PCL tunnel is distal to the ACL and meniscal root tunnels and in line with the ACL tunnel in the coronal plane. Patient rehabilitation for cruciate and collateral ligament injury is slowed by concomitant MRT as patients must remain non-weightbearing for 6 weeks postoperatively.
It is not uncommon for root tears to be associated with either traumatic or degenerative chondral defects, which can sometimes be significant and indicate one of various chondral procedures such as osteochondral autograft or allograft transplantation. Such repair of cartilaginous defects is typically reserved for lesions larger than 2 cm2, with smaller lesions having been shown to heal well with the use of less invasive techniques such as marrow venting. Rehabilitation is dependent on size and location of the lesion, which may necessitate 6 to 12 weeks of non- or toe-touch weightbearing and limited flexion to 45° for 4 to 6 weeks, which creates potential extension of recovery time to those healing from concomitant meniscal root repair.
Reconstruction of the meniscal root may be indicated when there is little or no tissue of the meniscal root remaining for appropriate fixation, which would lead either to over-tensioning of the meniscus in order to gain an anatomic repair, or insertion of posterior meniscal horn into the bony attachment site instead of the more ligamentous tissue of the meniscal root which has better biomechanical properties for use as an anchoring material. Medial meniscal posterior root reconstruction using gracilis tendon autograft has been described.
After harvest of a 4 mm diameter gracilis graft from the pes anserinus, the superficial MCL is released off the femur to increase working space. A tibial tunnel is drilled from the medial aspect of the tibial tuberosity to the prepared footprint of the medial meniscal root. A suture is then passed through the posterior horn remnant and used to shuttle the graft through the tunnel and ultimately provide end-to-end suture fixation of the posterior horn and gracilis tendon. The graft is fixed with a bioabsorbable screw with 30° to 45° knee flexion. Recovery and rehabilitation is similar to repair of MRT with the addition of possible donor-site morbidity.
Meniscal allograft transplantation may be used for selected meniscus-deficient patients, but has restrictive indications and is contraindicated in patients with instability, older age, axial malalignment, and diffuse subchondral bone exposure. These conditions may be corrected and render the patient into a suitable candidate for meniscal transplant, but although improved clinical outcomes have been reported with allograft transplantation there is a paucity of high-quality literature with adequate control groups. However, transplantation remains one of the few treatments for meniscus-deficient knees that may be considered before arthroplasty.
A wide variety of meniscal prosthetics has been investigated, with the most promising results occurring in porous, stiffer scaffolds that allow for the ingrowth of new cartilaginous tissue. This is usually achieved through seeding of the scaffold with fibrochondrocytes, autologous chondrocytes, hyaluronic acid, or human connective tissue growth factors. Other options have explored resorbable collagen meniscus implants made from bovine Achilles tendons, and improved meniscal scaffold fit via 3-dimensional printing. These various meniscal replacements most often suffer from transplant tear, malposition, and misshape, and are almost universally inferior to native meniscal tissue in tensile strength and compression.
Further comparative studies and improved methods are likely necessary in this field before it is widely used.
Offloading osteotomy
In patients with irreparable MRTs or meniscal-deficient knees in the presence of significant axial malalignment (>8°), the progression of degenerative changes may be slowed by offloading osteotomy. This may delay the need for knee arthroplasty for 15 or more years in 50% to 60% of patients.
Patients with increased BMI are at higher risk for failure with offloading osteotomy, and patient body habitus should be considered carefully. Trial of an unloader brace to simulate the effects of surgery may be useful to determine which patients will best benefit from this procedure.
It should be noted that use of osteotomy and associated hardware may increase the complexity of future arthroplasty should such become necessary by adding a hardware removal stage to the surgery, as well as increasing the difficulty to balance the knee.
Arthroplasty
The final solution for degenerative and otherwise irreparable changes in the knee is replacement via uni-compartmental or total knee arthroplasty. Although this option is frequently utilized and results in profound lifestyle improvement for appropriate patients, the expected life-span of arthroplastic prosthetics is limited and thus arthroplasty should be delayed as long as possible. For this reason, it is increasingly recognized among the orthopedic community that prevention of degeneration via meniscal repair, reconstruction, and salvage techniques is preferable as first-line treatment, and attitudes are continually shifting from meniscectomy to repair.
The primary goal of addressing MRTs is ultimately longevity of the patient's native knee function to maximize utility and quality of life while minimizing pain, instability, or mechanical symptoms. To that end, several subjective and objective outcome measures may be utilized including patient satisfaction, return to activities, progression of OA, and need for future interventions. Unfortunately, our ability to definitively describe these outcomes is limited by the somewhat recent advent of meniscal root repairs as a more common procedure, and the lack of long-term follow-up studies. What evidence does exist points strongly to the ability of meniscal root repairs to prevent further accelerated degeneration of the knee joint. Indeed, the results of several studies investigating transtibial repair outcomes estimated that progression of OA is halted in up to 84% of patients after transtibial repair.
Arthroscopic transtibial pullout repair for posterior medial meniscus root tears: a systematic review of clinical, radiographic, and second-look arthroscopic results.
Other investigators have reviewed literature comparing surgical repair to meniscectomy and nonoperative treatment over 39 months, and they similarly reported significantly less OA after surgical repair.
Meniscus root repair vs meniscectomy or nonoperative management to prevent knee osteoarthritis after medial meniscus root tears: clinical and economic effectiveness.
LaPrade et al demonstrated that subjective measures also show general patient satisfaction as measured with significant postoperative self-reported improvement and improved Lysholm, Tegner activity scale, and Western Ontario and McMaster Universities osteoarthritis index score.
Additionally, there was no reported difference in patient outcomes or satisfaction between medial and lateral root repairs, or for patients above or under the age of 50.
Meniscal root tears have a potentially devastating effect on rapid progression of tibiofemoral OA, as evidenced by up to 80% of SONK cases being associated with MRTs.
As previously mentioned, meniscal root repair results in slowed progression of OA compared to meniscectomy or nonoperative treatment. Indeed, Krivicich et al conducted a systematic review of patients 4 years out from surgical repair or meniscectomy for treatment for MRTs and found that patients with meniscectomy were 300% more likely to both have progression of their previously documented OA and to convert to total knee arthroplasty compared to patients receiving meniscal repair.
Comparison of long-term radiographic outcomes and rate and time for conversion to total knee arthroplasty between repair and meniscectomy for medial meniscus posterior root tears: a systematic review and meta-analysis.
More data are still needed to determine long-term prognosis of meniscal root repairs; however, short- and mid-term outcomes have provided fairly conclusive evidence that in that time frame repair is much more chondroprotective than meniscectomy or nonoperative treatment.
Pearls and pitfalls
1.
Medial collateral ligament release may be performed when adequate visualization of the posterior horn is not possible, particularly in those with tight medial compartments. Release of the MCL allows for instrumentation and visualization to perform the repair without damaging articular cartilage. The MCL is then treated nonoperatively.
2.
Low profile tibial fixation devices such as the EndoButton (Smith and Nephew) are less invasive and lead to fewer complications from symptomatic hardware than a screw and washer.
Decortication of the meniscal root attachment site prior to fixation aids in the growth of the meniscal root into the bone, increasing strength of the final construct.
Residual extrusion on postoperative MRI is not an uncommonly reported finding. It is thought to occur due to incomplete anatomic reduction of the root to its attachment site—often because reduction is hindered by scarring to the capsule over time.
Peripheral release of the meniscus from the joint capsule is useful especially in cases where chronic meniscal extrusion has led to scarring of the meniscal body to the capsule, making it difficult to reduce to its anatomic location. Because the meniscus scars back to the capsule after release during the non-weightbearing portion of patient recovery, this technique is thought to be quite effective and safe.
A peripheral stabilization suture is thought to help reduce meniscal extrusion postoperatively, aiding in scarring of the meniscus in a more anatomic location.
Robert F. LaPrade reports a relationship with Twin Cities Orthopedics that includes: employment. Nicholas I. Kennedy reports a relationship with Twin Cities Orthopedics that includes: employment. Morgan D. Homan reports a relationship with Twin Cities Orthopedics that includes: employment. Robert F. LaPrade reports a relationship with Arthrex Inc that includes: consulting or advisory and travel reimbursement. Robert F. LaPrade reports a relationship with Smith and Nephew Inc that includes: consulting or advisory. Robert F. LaPrade reports a relationship with US Department of Defense that includes: funding grants. Robert F. LaPrade reports a relationship with National Institutes of Health that includes: funding grants. Robert F. LaPrade reports a relationship with Journal of Knee Surgery that includes: board membership. Robert F. LaPrade reports a relationship with Knee Surgery, Sports Traumatology, Arthroscopy (KSSTA) that includes: board membership. Nicholas I. Kennedy reports a relationship with Video Journal of Sports Medicine that includes: board membership. Robert F. LaPrade has patent with royalties paid to Arthrex.
Ethics approval
The authors declare that informed patient consent was not provided because there is no patient information in this study which requires the need for informed consent. All images used for illustrative purposes are completely de-identified, and this review of current literature concepts did not utilize primary patient data.
References
Steineman B.D.
LaPrade R.F.
Santangelo K.S.
Warner B.T.
Goodrich L.R.
Haut Donahue T.L
Early osteoarthritis after untreated anterior meniscal root tears: an in vivo animal study.
Altered tibiofemoral contact mechanics due to lateral meniscus posterior horn root avulsions and radial tears can be restored with in situ pull-out suture repairs.
Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site: in situ pull-out repair restores derangement of joint mechanics.
Clinical and radiological outcomes of meniscal repair versus partial meniscectomy for medial meniscus root tears: a systematic review and meta-analysis.
Utilization of transtibial centralization suture best minimizes extrusion and restores tibiofemoral contact mechanics for anatomic medial meniscal root repairs in a cadaveric model.
Epidemiology of combined injuries of the secondary stabilizers in ACL-deficient knees: medial meniscal ramp lesion, lateral meniscus root tear, and all tear: a prospective case series of 602 patients with ACL tears from the SANTI Study Group.
Arthroscopic transtibial pullout repair for posterior medial meniscus root tears: a systematic review of clinical, radiographic, and second-look arthroscopic results.
Suture anchor repair for a medial meniscus posterior root tear combined with arthroscopic meniscal centralization and open wedge high tibial osteotomy.
Optimal tibial tunnel placement for medial and lateral meniscus root repair on the anteromedial tibia in the setting of anterior and posterior cruciate ligament reconstruction of the knee.
Meniscus root repair vs meniscectomy or nonoperative management to prevent knee osteoarthritis after medial meniscus root tears: clinical and economic effectiveness.
Comparison of long-term radiographic outcomes and rate and time for conversion to total knee arthroplasty between repair and meniscectomy for medial meniscus posterior root tears: a systematic review and meta-analysis.
Graphic displaying an example of each type of meniscal root tear as described by the LaPrade classification system. A Type 2A tear is depicted as an example for a Type 2 tear. Reproduced with permission from LaPrade et al.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References
Sagittal magnetic resonance imaging demonstrating the “ghost sign,” where the normal signal for the posterior meniscal root is absent (dotted outline).
Normal position for a surgical button (white arrow) over the anterior transtibial tunnel aperture for root repair (left) compared with a modified transtibial position marked by the surgical button (white arrow) following proximal tibial osteotomy (right).
Recent interest has uncovered the importance of understanding meniscal root anatomy, its effect on biomechanics of the knee joint, and appropriate treatment modalities. Meniscal root tears may account for up to one-fifth of all meniscal tears and have downstream consequences that can be as severe as total meniscectomy due to the unique force-dispersing properties of the meniscus. Meniscal biomechanics rely heavily upon the integrity of root attachments, and this historically overlooked etiology of knee pain and early onset osteoarthritis plays a vital role in maintaining the longevity of the knee joint. As meniscal root pathology becomes more commonly known and clinically assessed, an understanding of classifications, repair methods, and indications is important for surgeons.
Historically overlooked as an etiology of knee pain and early onset osteoarthritis (OA), the meniscal root plays a vital role in maintaining the longevity of the knee joint.1x1Steineman, B.D., LaPrade, R.F., Santangelo, K.S., Warner, B.T., Goodrich, L.R., and Haut Donahue, T.L. Early osteoarthritis after untreated anterior meniscal root tears: an in vivo animal study. Orthop J Sports Med. 2017;
5: 2325967117702452https://doi.org/10.1177/2325967117702452 Crossref | PubMed | Scopus (19) | Google ScholarSee all References,2x2Floyd, E.R., Rodriguez, A.N., Falaas, K.L. et al. The natural history of medial meniscal root tears: a biomechanical and clinical case perspective. Front Bioeng Biotechnol. 2021;
9: 744065https://doi.org/10.3389/fbioe.2021.744065 Crossref | PubMed | Scopus (4) | Google ScholarSee all References Reported to affect nearly 100,000 patients annually, meniscal root tears (MRTs) account for up to 10% to 21% of all meniscal tears and have been labeled as a “silent epidemic” due to their widespread underdiagnosis and the rapid progression of untreated injuries to OA.3x3LaPrade, R.F., Floyd, E.R., Carlson, G.B., Moatshe, G., Chahla, J., and Monson, J.K. Meniscal root tears: solving the silent epidemic. J Arthrosc Surg Sports Med. 2021;
2: 47–57https://doi.org/10.25259/jassm_55_2020 Crossref | Google ScholarSee all References,4x4LaPrade, C.M., Jansson, K.S., Dornan, G., Smith, S.D., Wijdicks, C.A., and LaPrade, R.F. Altered tibiofemoral contact mechanics due to lateral meniscus posterior horn root avulsions and radial tears can be restored with in situ pull-out suture repairs. J Bone Joint Surg Am. 2014;
96: 471–479https://doi.org/10.2106/JBJS.L.01252 Crossref | PubMed | Scopus (190) | Google ScholarSee all References,5x5Cinque, M.E., DePhillipo, N.N., Moatshe, G. et al. Clinical outcomes of inside-out meniscal repair according to anatomic zone of the meniscal tear. Orthop J Sports Med. 2019;
7: 2325967119860806https://doi.org/10.1177/2325967119860806 Crossref | PubMed | Scopus (29) | Google ScholarSee all References,6x6Bonasia, D.E., Pellegrino, P., D'Amelio, A., Cottino, U., and Rossi, R. Meniscal root tear repair: why, when and how?. Orthop Rev (Pavia). 2015;
7: 5792https://doi.org/10.4081/or.2015.5792 Crossref | PubMed | Scopus (42) | Google ScholarSee all References Demographic differences have been reported for types of MRTs, with young male patients more likely to present with lateral MRTs, often in the setting of multiple ligament knee injuries, knee trauma, or concomitant anterior cruciate ligament (ACL) tears.7x7Cinque, M.E., Chahla, J., Moatshe, G., Faucett, S.C., Krych, A.J., and LaPrade, R.F. Meniscal root tears: a silent epidemic. Br J Sports Med. 2018;
52: 872–876https://doi.org/10.1136/bjsports-2017-098942 Crossref | PubMed | Scopus (28) | Google ScholarSee all References Medial MRTs often occur via a low-energy mechanism and are more common in older patients with higher body mass index (BMI) and existing degenerative changes in the knee.8x8Brophy, R.H., Wojahn, R.D., Lillegraven, O., and Lamplot, J.D. Outcomes of arthroscopic posterior medial meniscus root repair: association with body mass index. J Am Acad Orthop Surg. 2019;
27: 104–111https://doi.org/10.5435/jaaos-D-17-00065 Crossref | PubMed | Scopus (0) | Google ScholarSee all References,9x9Krych, A.J., Bernard, C.D., Kennedy, N.I. et al. Medial versus lateral meniscus root tears: is there a difference in injury presentation, treatment decisions, and surgical repair outcomes?. Arthroscopy. 2020;
36: 1135–1141https://doi.org/10.1016/j.arthro.2019.11.098 Abstract | Full Text | Full Text PDF | PubMed | Scopus (27) | Google ScholarSee all References
The medial and lateral menisci form 2 C-shaped borders filling the triangular space between the tibial and femoral articular cartilage surfaces and the joint capsule. The meniscus itself is roughly the shape of a collapsed triangle on cross section, with a broad, vascular outside body which thins to a less vascular and then ultimately avascular apical ridge between chondral surfaces. This unique space-filling shape leads to increased joint-surface contact area.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,23x23Laprade, R.F., Floyd, E.R., Carlson, G.B., Moatshe, G., Chahla, J., and Monson, J.K. Meniscal root tears: solving the silent epidemic. J Arthrosc Surg Sports Med. 2020;
2: 47–57https://doi.org/10.25259/JASSM_55_2020 Crossref | Google ScholarSee all References The lateral meniscus is smaller and more circular with its anterior and posterior roots nearly meeting at the lateral intercondylar eminence. Both anterior and posterior medial meniscal roots lie peripheral to the lateral root insertions, forming more of a horseshoe or C shape.
The medial meniscus, perhaps due to the greater percentage of weightbearing through the medial femoral and tibial pillars, is more rigidly attached to the tibia and the surrounding capsule, and therefore, less mobile. The medial meniscus therefore provides a certain measure of stability for the femoral condyle on the tibia—a sort of shallow, rounded cup holder. The lateral meniscus in comparison has more laxity allowing a small amount of anteroposterior glide along the tibial surface so as to better move with the lateral femoral condyle during natural axial rotation about the tibiofemoral joint. Much of the posterior horn of the lateral meniscus lacks meniscocapsular attachments, thereby allowing this increased mobility. However, the meniscofemoral ligaments, which course from the medial most extent of the posterior horn to their attachment sites in the femoral notch both anterior and posterior to the bundles of the Posterior cruciate ligament (PCL), both confer notable stability namely to internal rotation and anterior translational forces.
While the meniscocapsular attachments and meniscofemoral ligaments are both important for meniscal stability, the most biomechanically important connections are the meniscal root attachments.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,22x22Aspden, R.M., Yarker, Y.E., and Hukins, W.L. Collagen orientations in the meniscus of the knee joint. J Anat. 1985;
140: 371–380 PubMed | Google ScholarSee all References,23x23Laprade, R.F., Floyd, E.R., Carlson, G.B., Moatshe, G., Chahla, J., and Monson, J.K. Meniscal root tears: solving the silent epidemic. J Arthrosc Surg Sports Med. 2020;
2: 47–57https://doi.org/10.25259/JASSM_55_2020 Crossref | Google ScholarSee all References Furthermore, meniscal root integrity is crucial to meniscal function as a whole, because the disruption of these anchoring sites releases the circular tension holding the meniscus between the tibiofemoral cartilages.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References The resulting axial compression through the tibiofemoral joint then pushes the meniscus out of the articular joint space, thereby diminishing the ability of the meniscus to adequately disperse axial tibiofemoral joint forces.
Biomechanics, stability, and sequalae
Foundational studies examining the biomechanical and structural characteristics of the menisci have established their critical role in modulating force transmission across the tibiofemoral articulation.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,21x21Bhatia, S., LaPrade, C.M., Ellman, M.B., and LaPrade, R.F. Meniscal root tears: significance, diagnosis, and treatment. Am J Sports Med. 2014;
42: 3016–3030https://doi.org/10.1177/0363546514524162 Crossref | PubMed | Scopus (295) | Google ScholarSee all References,22x22Aspden, R.M., Yarker, Y.E., and Hukins, W.L. Collagen orientations in the meniscus of the knee joint. J Anat. 1985;
140: 371–380 PubMed | Google ScholarSee all References Classically, the meniscus has been likened to a “shock absorber” in the knee.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,23x23Laprade, R.F., Floyd, E.R., Carlson, G.B., Moatshe, G., Chahla, J., and Monson, J.K. Meniscal root tears: solving the silent epidemic. J Arthrosc Surg Sports Med. 2020;
2: 47–57https://doi.org/10.25259/JASSM_55_2020 Crossref | Google ScholarSee all References It functions in this capacity by converting axial compressive loads into radial tangential “hoop stresses.”17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,22x22Aspden, R.M., Yarker, Y.E., and Hukins, W.L. Collagen orientations in the meniscus of the knee joint. J Anat. 1985;
140: 371–380 PubMed | Google ScholarSee all References In doing so, the menisci reduce the total compressive forces experienced by the chondral cartilage of the tibial plateau and femoral condyles.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,22x22Aspden, R.M., Yarker, Y.E., and Hukins, W.L. Collagen orientations in the meniscus of the knee joint. J Anat. 1985;
140: 371–380 PubMed | Google ScholarSee all References Furthermore, by increasing the contact surface area of the tibiofemoral articulation, the menisci function to spread compressive loads over a larger surface area, thereby avoiding the phenomenon of “point loading.” This dispersion of axial compressive loads across the knee helps to provide long-term protective effects to chondral surfaces and prevent progression of osteoarthritic changes.1x1Steineman, B.D., LaPrade, R.F., Santangelo, K.S., Warner, B.T., Goodrich, L.R., and Haut Donahue, T.L. Early osteoarthritis after untreated anterior meniscal root tears: an in vivo animal study. Orthop J Sports Med. 2017;
5: 2325967117702452https://doi.org/10.1177/2325967117702452 Crossref | PubMed | Scopus (19) | Google ScholarSee all References In addition, the loss of stability caused by root tears leads to increased instability and motion across the tibiofemoral articulation, which puts increased strain on stabilizing ligaments such as the ACL.24x24Samuelsen, B.T., Aman, Z.S., Kennedy, M.I. et al. Posterior medial meniscus root tears potentiate the effect of increased tibial slope on anterior cruciate ligament graft forces. Am J Sports Med. 2020;
48: 334–340https://doi.org/10.1177/0363546519889628 Crossref | PubMed | Scopus (18) | Google ScholarSee all References It may also be that increased motion due to instability inferred by meniscal root pathology changes the biomechanics of the tibiofemoral joint to an extent that expedites the joint degradation sustained.
Pathology discussing diagnosis
LaPrade classification of meniscal root tears
The term MRT is used to describe damage occurring to one of the meniscal attachment sites within 1 cm from the meniscal root insertion.1x1Steineman, B.D., LaPrade, R.F., Santangelo, K.S., Warner, B.T., Goodrich, L.R., and Haut Donahue, T.L. Early osteoarthritis after untreated anterior meniscal root tears: an in vivo animal study. Orthop J Sports Med. 2017;
5: 2325967117702452https://doi.org/10.1177/2325967117702452 Crossref | PubMed | Scopus (19) | Google ScholarSee all References,17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,23x23Laprade, R.F., Floyd, E.R., Carlson, G.B., Moatshe, G., Chahla, J., and Monson, J.K. Meniscal root tears: solving the silent epidemic. J Arthrosc Surg Sports Med. 2020;
2: 47–57https://doi.org/10.25259/JASSM_55_2020 Crossref | Google ScholarSee all References Meniscal root tears can manifest in a variety of ways, necessitating the use of an appropriate classification system. The LaPrade classification for MRTs classifies MRTs based on the location and quality of the tear.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References
Unlike other proposed systems for classifying MRTs, the LaPrade classification for MRTs applies to both the anterior and posterior roots and separates tears into 5 types (Fig. 1Fig. 1).12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References,17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References Type 1 describes an isolated, stable partial tear of the meniscal root.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References Type 2 describes a complete radial tear of the meniscal root and contains 3 subtypes which differ based on their location along the meniscal root relative to the center of the root insertion; Type 2A occurs at less than 3 mm from the center of the root attachment, Type 2B occurs from 3 to 6 mm from the center of the root attachment site, Type 2C occurs from 6 to 9 mm from the center of the root attachment site.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References Type 3 describes an MRT with a concomitant longitudinal/circumferential tear (commonly referred to as a “bucket handle” tear).12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References Type 4 describes an oblique tear of the meniscus that extends into the meniscal root resulting in complete root detachment.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References Finally, Type 5 describes the case of a complete bony avulsion fracture of the root from its attachment to the tibial plateau.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References
Fig. 1
Graphic displaying an example of each type of meniscal root tear as described by the LaPrade classification system. A Type 2A tear is depicted as an example for a Type 2 tear. Reproduced with permission from LaPrade et al.12x12LaPrade, C.M., James, E.W., Cram, T.R., Feagin, J.A., Engebretsen, L., and LaPrade, R.F. Meniscal root tears: a classification system based on tear morphology. Am J Sports Med. 2015;
43: 363–369https://doi.org/10.1177/0363546514559684 Crossref | PubMed | Scopus (196) | Google ScholarSee all References
Many studies have shown that the meniscus-deficient knee (eg, patients treated with meniscectomy or hemi-meniscectomy) almost always consistently and rapidly progresses to OA.1x1Steineman, B.D., LaPrade, R.F., Santangelo, K.S., Warner, B.T., Goodrich, L.R., and Haut Donahue, T.L. Early osteoarthritis after untreated anterior meniscal root tears: an in vivo animal study. Orthop J Sports Med. 2017;
5: 2325967117702452https://doi.org/10.1177/2325967117702452 Crossref | PubMed | Scopus (19) | Google ScholarSee all References,25x25LaPrade, R.F. Not your father's (or mother's) meniscus surgery. Minn Med. 2007;
: 41–43 PubMed | Google ScholarSee all References Furthermore, biomechanical models have shown the meniscal root-deficient knee to be biomechanically equivalent to the meniscectomized knee, and therefore, pose a similarly significant risk of progression to fulminant OA.16x16Allaire, R., Muriuki, M., Gilbertson, L., and Harner, C.D. Biomechanical consequences of a tear of the posterior root of the medial meniscus. Similar to total meniscectomy. J Bone Joint Surg Am. 2008;
90: 1922–1931https://doi.org/10.2106/JBJS.G.00748 Crossref | PubMed | Scopus (608) | Google ScholarSee all References,17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References Studies have further demonstrated that nonanatomic repair of an MRT functions biomechanically similar to leaving the root left untreated and thereby would have significant long-term degenerative effects.26x26LaPrade, C.M., Foad, A., Smith, S.D. et al. Biomechanical consequences of a nonanatomic posterior medial meniscal root repair. Am J Sports Med. 2015;
43: 912–920https://doi.org/10.1177/0363546514566191 Crossref | PubMed | Scopus (132) | Google ScholarSee all References,27x27Steineman, B.D., LaPrade, R.F., and Haut Donahue, T.L. Nonanatomic placement of posteromedial meniscal root repairs: a finite element study. J Biomech Eng. 2020;
142: 081004https://doi.org/10.1115/1.4045893 Crossref | PubMed | Scopus (5) | Google ScholarSee all References This is because the chondroprotective functions of the menisci are ultimately dependent upon their attachment to their respective anatomic root attachment sites.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,21x21Bhatia, S., LaPrade, C.M., Ellman, M.B., and LaPrade, R.F. Meniscal root tears: significance, diagnosis, and treatment. Am J Sports Med. 2014;
42: 3016–3030https://doi.org/10.1177/0363546514524162 Crossref | PubMed | Scopus (295) | Google ScholarSee all References,28x28Pache, S., Aman, Z.S., Kennedy, M. et al. Meniscal root tears: current concepts review. Arch Bone Jt Surg. 2018;
6: 250–259 PubMed | Google ScholarSee all References When the native menisci experience axial compressive forces, they are placed into circular traction.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,22x22Aspden, R.M., Yarker, Y.E., and Hukins, W.L. Collagen orientations in the meniscus of the knee joint. J Anat. 1985;
140: 371–380 PubMed | Google ScholarSee all References,28x28Pache, S., Aman, Z.S., Kennedy, M. et al. Meniscal root tears: current concepts review. Arch Bone Jt Surg. 2018;
6: 250–259 PubMed | Google ScholarSee all References However, when the MRTs are compromised, the meniscus is unable to retain circular traction, and instead, extrudes out of the joint space.17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,21x21Bhatia, S., LaPrade, C.M., Ellman, M.B., and LaPrade, R.F. Meniscal root tears: significance, diagnosis, and treatment. Am J Sports Med. 2014;
42: 3016–3030https://doi.org/10.1177/0363546514524162 Crossref | PubMed | Scopus (295) | Google ScholarSee all References,28x28Pache, S., Aman, Z.S., Kennedy, M. et al. Meniscal root tears: current concepts review. Arch Bone Jt Surg. 2018;
6: 250–259 PubMed | Google ScholarSee all References As a result, the meniscus is unable to disperse axial compressive loads, and point loading occurs.15x15Padalecki, J.R., Jansson, K.S., Smith, S.D. et al. Biomechanical consequences of a complete radial tear adjacent to the medial meniscus posterior root attachment site: in situ pull-out repair restores derangement of joint mechanics. Am J Sports Med. 2014;
42: 699–707https://doi.org/10.1177/0363546513499314 Crossref | PubMed | Scopus (188) | Google ScholarSee all References Point loading results in a phenomenon described previously as spontaneous osteonecrosis of the knee (SONK, now thought to be more appropriately referred to as “subchondral insufficiency fracture,” or SIFK), which is one of the identifiable signs of an MRT that can be found on magnetic resonance imaging (MRI).17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References,29x29Hussain, Z.B., Chahla, J., Mandelbaum, B.R., Gomoll, A.H., and LaPrade, R.F. The role of meniscal tears in spontaneous osteonecrosis of the knee: a systematic review of suspected etiology and a call to revisit nomenclature. Am J Sports Med. 2019;
47: 501–507https://doi.org/10.1177/0363546517743734 Crossref | PubMed | Scopus (54) | Google ScholarSee all References Therefore, strategies to minimize meniscal extrusion following meniscal root repair have also become an area of great focus.29x29Hussain, Z.B., Chahla, J., Mandelbaum, B.R., Gomoll, A.H., and LaPrade, R.F. The role of meniscal tears in spontaneous osteonecrosis of the knee: a systematic review of suspected etiology and a call to revisit nomenclature. Am J Sports Med. 2019;
47: 501–507https://doi.org/10.1177/0363546517743734 Crossref | PubMed | Scopus (54) | Google ScholarSee all References,30x30Dean, R.S., DePhillipo, N.N., Monson, J.K., and LaPrade, R.F. Peripheral stabilization suture to address meniscal extrusion in a revision meniscal root repair: surgical technique and rehabilitation protocol. Arthrosc Tech. 2020;
9: e1211–e1218https://doi.org/10.1016/j.eats.2020.04.022 Abstract | Full Text | Full Text PDF | PubMed | Scopus (10) | Google ScholarSee all References,31x31Daney, B.T., Aman, Z.S., Krob, J.J. et al. Utilization of transtibial centralization suture best minimizes extrusion and restores tibiofemoral contact mechanics for anatomic medial meniscal root repairs in a cadaveric model. Am J Sports Med. 2019;
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Diagnostic pearls
Due to the acceleration of joint degeneration caused by MRTs, early diagnosis and prompt treatment is paramount for good outcomes. The clinical diagnosis begins with a detailed patient history and physical examination, and while certain radiographic findings may raise clinical suspicion, the gold standard for diagnosis is ultimately MRI and arthroscopy. Regarding the notoriety of MRTs as missed diagnoses, high clinical suspicion is required for the diagnosis, and clinician understanding of etiology and diagnostic signs is crucial.
History and physical examination
The difficulty of diagnosing MRTs stems in part from the lack of similarity to injury of the meniscal body. It has been reported, for example, that only 10% to 15% of patients with medial posterior root tears exhibit signs of knee locking or giving way.32x32Lee, D.W., Ha, J.K., and Kim, J.G. Medial meniscus posterior root tear: a comprehensive review. Knee Surg Relat Res. 2014;
26: 125–134https://doi.org/10.5792/ksrr.2014.26.3.125 Crossref | PubMed | Scopus (70) | Google ScholarSee all References Indeed, similar to the majority of chronic meniscal injuries in older populations, up to 70% of patients cannot recall a direct inciting injury.33x33Kim, J.H., Chung, J.H., Lee, D.H., Lee, Y.S., Kim, J.R., and Ryu, K.J. Arthroscopic suture anchor repair versus pullout suture repair in posterior root tear of the medial meniscus: a prospective comparison study. Arthroscopy. 2011;
27: 1644–1653https://doi.org/10.1016/j.arthro.2011.06.033 Abstract | Full Text | Full Text PDF | PubMed | Scopus (155) | Google ScholarSee all References When present, the mechanism of injury may lead to clinical suspicion of a root tear, such as a rotatory blow to a flexed knee which is assumed to be a common etiology. The presence of an ACL injury should also prompt examination for an MRT, most commonly in the lateral posterior root. Lateral meniscus root tears have been reported to have an incidence rate ranging from 2.65% to 16% in ACL injuries.34x34Magosch, A., Mouton, C., Nührenbörger, C., and Seil, R. Medial meniscus ramp and lateral meniscus posterior root lesions are present in more than a third of primary and revision ACL reconstructions. Knee Surg Sports Traumatol Arthrosc. 2021;
29: 3059–3067https://doi.org/10.1007/s00167-020-06352-3 Crossref | PubMed | Scopus (27) | Google ScholarSee all References,35x35Gracia, G., Cavaignac, M., Marot, V., Mouarbes, D., Laumonerie, P., and Cavaignac, E. Epidemiology of combined injuries of the secondary stabilizers in ACL-deficient knees: medial meniscal ramp lesion, lateral meniscus root tear, and all tear: a prospective case series of 602 patients with ACL tears from the SANTI Study Group. Am J Sports Med. 2022;
50: 1843–1849https://doi.org/10.1177/03635465221092767 Crossref | PubMed | Scopus (5) | Google ScholarSee all References Physical examination is also limited in diagnostic utility, with some combination of pain with deep flexion (for posterior root tears), palpable meniscal extrusion, and a positive McMurray's test being present in only 50% to 60% of patients.36x36James, E., Cinque, M., Chahla, J., and LaPrade, R. An evidence-based approach to the diagnosis and treatment of meniscal root tears. Min Ortop Traumatol. 2017;
68https://doi.org/10.23736/S0394-3410.17.03805-X Crossref | Scopus (4) | Google ScholarSee all References Physician gestalt after history and physical should direct further diagnostic imaging.
Imaging
Plain film radiographs including Rosenberg view are commonly obtained in orthopedic clinics; these images are less helpful for characterizing type of meniscal pathology and instead more helpful with inferring chronicity and severity of degenerative changes. Because root tears are structurally comparable to meniscal deficiency, the onset of rapid arthritic changes and increased Kellgren-Lawrence scores, particularly in young patients, should provoke investigation for MRTs. Long leg standing films should be acquired to assess coronal alignment as well. More recent literature has demonstrated that varus malalignment of >5° is associated with slightly decreased outcome scores compared with neutral alignment.37x37Ridley, T.J., Ruzbarsky, J.J., Dornan, G.J. et al. Minimum 2-year clinical outcomes of medial meniscus root tears in relation to coronal alignment. Am J Sports Med. 2022;
50: 1254–1260https://doi.org/10.1177/03635465221080167 Crossref | PubMed | Scopus (2) | Google ScholarSee all References However, patients still have low failure rate and good improvements in outcome scores with varus alignment following meniscal root repair. Furthermore, concomitant osteotomy in this population was associated with significantly worse outcomes and therefore is no longer recommended in this patient cohort.
MRI is the most reliable noninvasive test for MRTs. Although in the past, studies had demonstrated specificity as low as 70%,38x38Ozkoc, G., Circi, E., Gonc, U., Irgit, K., Pourbagher, A., and Tandogan, R.N. Radial tears in the root of the posterior horn of the medial meniscus. Knee Surg Sports Traumatol Arthrosc. 2008;
16: 849–854https://doi.org/10.1007/s00167-008-0569-z Crossref | PubMed | Scopus (181) | Google ScholarSee all References the literature now reports recent diagnostic advances have improved predictive values to over 90%.39x39De Smet, A.A. and Mukherjee, R. Clinical, MRI, and arthroscopic findings associated with failure to diagnose a lateral meniscal tear on knee MRI. AJR Am J Roentgenol. 2008;
190: 22–26https://doi.org/10.2214/ajr.07.2611 Crossref | PubMed | Scopus (0) | Google ScholarSee all References,40x40LaPrade, R.F., Ho, C.P., James, E., Crespo, B., LaPrade, C.M., and Matheny, L.M. Diagnostic accuracy of 3.0 T magnetic resonance imaging for the detection of meniscus posterior root pathology. Knee Surg Sports Traumatol Arthrosc. 2015;
23: 152–157https://doi.org/10.1007/s00167-014-3395-5 Crossref | PubMed | Scopus (67) | Google ScholarSee all References,41x41Choi, S.H., Bae, S., Ji, S.K., and Chang, M.J. The MRI findings of meniscal root tear of the medial meniscus: emphasis on coronal, sagittal and axial images. Knee Surg Sports Traumatol Arthrosc. 2012;
20: 2098–2103https://doi.org/10.1007/s00167-011-1794-4 Crossref | PubMed | Scopus (86) | Google ScholarSee all References Signs of MRTs on MRI include increased signal resulting from fluid collection near the meniscal roots (Fig. 2Fig. 2), the ghost sign (sagittal cuts on which the meniscus is not identifiable in its normal position, Fig. 3Fig. 3), and coronal views showing meniscal extrusion greater than 3 mm from the tibial articular cartilage (Fig. 4Fig. 4).17x17Banovetz, M.T., Roethke, L.C., Rodriguez, A.N., and LaPrade, R.F. Meniscal root tears: a decade of research on their relevant anatomy, biomechanics, diagnosis, and treatment. Arch Bone Jt Surg. 2022;
10: 366–380https://doi.org/10.22038/ABJS.2021.60054.2958 Crossref | PubMed | Scopus (3) | Google ScholarSee all References Axial cuts can similarly be quite telling and representative of an MRT if the imaging cuts demonstrated have a good on-profile view of the root attachment (Fig. 5Fig. 5). Associated SONK, a misnomer more properly replaced with SIFK, is bony edema of the femoral condyles or tibial plateau thought to be caused by increased point-loading due to lack of meniscal support. This is another MRI finding that, in the absence of obvious causes, should prompt further investigation of an MRT.28x28Pache, S., Aman, Z.S., Kennedy, M. et al. Meniscal root tears: current concepts review. Arch Bone Jt Surg. 2018;
6: 250–259 PubMed | Google ScholarSee all References
Article Info
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