At Issue

Medial meniscal root tears: Fix it or leave it alone

Question: In your opinion, when do you fix medial meniscal root tears? When do you leave them alone?

Proper diagnosis yields higher patient satisfaction after medial meniscal root repair

Medial and lateral menisci are crescent-shaped fibrocartilage structures that provide joint congruity, stabilization and lubrication and act as “shock absorbers” for joint preservation. During weight-bearing activities, the menisci dissipate axial loads and contain hoop stresses. The medial meniscus transmits approximately 50% of the total joint load of the knee medial compartment, thus protecting the articular cartilage from excessive force.

Matthew H. Blake

Matthew H. Blake

Darren L. Johnson

Darren L. Johnson

Tears to the medial meniscal root change the biomechanics and kinematics of the knee, which cause early degeneration of the joint. It has been shown the peak tibiofemoral contact pressure after a total meniscectomy is equal to a posterior medial meniscal root tear.

Recent kinematic/biomechanical studies have also shown the importance of the medial meniscus to anterior translation of the knee. Absence of the medial meniscus (entire medial meniscal root tear) places large stresses on the ACL, the primary ligament that prevents anterior translation of the knee.

Diagnosis

Coronal MRI of posterior medial meniscal root tear
Coronal MRI shows a posterior medial meniscal root tear.
Sagittal MRI shows the “ghost sign
This sagittal MRI shows the “ghost sign."
Axial MRI shows a posterior medial meniscal root tear
Axial MRI shows a posterior medial meniscal root tear.
Posterior medial meniscal root tear
A posterior medial meniscal root tear is shown.
Images: Johnson DL

Making a medial meniscal root tear diagnosis is difficult because the typical history of locking, catching or giving way is less likely to be present. More often, the patient will complain of joint line pain with a minor traumatic event, such as squatting. Likewise, physical exam findings of an effusion, a positive McMurray test and a positive Apley grind test are not usually present.

The most commonly encountered signs are posterior knee pain with deep flexion and joint line tenderness. Another exam finding is palpating the anteromedial joint line, while placing a varus stress on a fully extended knee and feeling for meniscal extrusion. This extrusion should disappear without stress.

Coronal MRI sequences are generally considered the best images for visualization of medial meniscal root tears (Figure 1). While visualization of the meniscal root may be difficult due to MRI slice size, type of MRI and strength of MRI, an extrusion larger than 3 mm highly correlates with a root tear. The “ghost sign” or absence of an identifiable meniscus anterior to the posterior cruciate ligament is also indicative of a root tear (Figure 2). Depending on the cut thickness, axial MRI images may display the root tear (Figure 3).

Treatment

Historically, medial meniscal root tears have been treated conservatively or by partial meniscectomy. With advances in surgical techniques and instrumentation, meniscal root repair is a viable option that can restore the biomechanics and kinematics of the knee (Figure 4). Although a successful outcome of a meniscal root repair is predicated upon appropriate indications for the repair, not all medial meniscal root tears should be repaired.

PAGE BREAK

Medial meniscal root tears are more frequently diagnosed in patients who are older than 40 years, are overweight and cannot recall an inciting event. Radiographs may or may not show medial joint space narrowing. In addition to the root tear, the MRI often shows chondral loss or fissuring, other areas of meniscal tearing, bone marrow edema or osteophyte formation (Figure 5).

We believe these tears are more degenerative in nature, and there is no evidence to support that by repairing these medial meniscal root tears, knee degeneration will be postponed or stopped. It seems that in the above knee, the biology of the medial compartment has gone off the ski slope in a degenerative fashion and reversing that ski slope fall seems to be unproven at this time, particularly in the patient with low functional demands, who is older than 40 years and who has a BMI greater than 30. We have also seen complete meniscal root avulsions in the cruciate ligament-injured knee with complete injury of the medial ligament and posterior oblique ligament that opens in full extension. It is important that these root avulsions are anatomically repaired back to the bone. The anatomic landmark for repair is anterior to the PCL footprint on the tibia.

The ideal candidate for a medial meniscal root repair is an individual younger than 40 years who presents after an acute, traumatic event with a BMI less than 30 and a MRI that shows a medial meniscal root tear without secondary signs of osteoarthrosis or varus malalignment. However, these patients are rare. A case also can be made for medial meniscal root repairs for a symptomatic acute and possibly a chronic medial meniscal root tear in a non-obese patient older than 40 years with a MRI that does not have early arthritic changes. We believe that by repairing these tears, the degenerative process may be delayed or halted (Figure 6).

MRI with abundant subcutaneous fat
A MRI with abundant subcutaneous fat, horizontal meniscal tear, loss of medial compartment articular cartilage, bone marrow edema of femur and tibia is shown (a). A MRI with abundant fat, horizontal medial meniscal tear and medial meniscus root tear is shown (b).
posterior medial meniscal root repair
Shown is a posterior medial meniscal root repair.

The medial meniscus is an important secondary stabilizer of the knee. Knees with a deficient medial meniscus and an ACL tear have an increased anterior tibial translation of about 60% at 90° of flexion. It has been reported that the force experienced by the medial meniscus in the ACL-deficient knee increased by 52% in full extension and by 197% at 60° of flexion under a 134-N load. Reciprocally, an increased force is also placed on an ACL graft with a deficient medial meniscus. As such, it is critical to repair medial meniscal root tears during ACL reconstruction to help stabilize the knee, as well as to decrease stresses that the graft experiences.

Summary

The medial meniscus is an important structure that provides stability, dissipates force and assists to provide normal kinematics of the knee. Tears of the posterior medial meniscal root have shown to disrupt the normal motion of the knee, resulting in degenerative arthritis.

New surgical advances allow surgeons to repair these tears. Successful outcome and patient satisfaction after medial meniscal root repair are established initially upon appropriate diagnosis and patient selection.

Disclosures: Blake and Johnson report no relevant financial disclosures.

PAGE BREAK

Surgical intervention of medial meniscal root tears preserves joint function

Medial meniscal root tears are “radial” tears within 1 cm of the meniscal root insertion or an avulsion of the insertion of the meniscus. These injuries have been reported to change joint loading due to failure of the meniscus to convert axial loads into hoop stresses. This leads to decreased contact area and increased contact pressure and ultimately results in joint overloading and degenerative changes in the knee similar to a total meniscectomy state. This tear pattern was historically unrecognized, although more recently it has been suggested this “hidden” pathology may account for nearly 80% of the total knee replacements in patients younger than 60 years. Biomechanical studies have demonstrated that repair of medial meniscus posterior root tears leads to improved contact mechanics. Studies have also reported that patients who underwent a repair of the posterior root in the medial meniscus slowed the progression of arthritic changes compared with those who had a meniscectomy; although, this did not completely prevent the arthritic changes.

Jorge Chahla

Jorge Chahla

Andrew G. Geeslin

Andrew G. Geeslin

Robert F. LaPrade
Robert F. LaPrade

Posterior medial meniscal root tears are often times degenerative, but these can also occur with multi-ligament knee injuries in the acute setting. In addition, focal chondral lesions occur more commonly with medial than lateral-sided injuries. Non-anatomic placement of a PCL reconstruction tibial tunnel is a reported cause of iatrogenic medial meniscal posterior root tears. Identification of a meniscal root tear on MRI may be challenging due to the relatively small size of the root. However, coronal sections may reveal the presence of meniscal extrusion or vertical defects, and sagittal sections may reveal the “ghost sign” (absence of an identifiable meniscus or increased signal replacing the normal hypointense signal of meniscal tissue). These imaging pearls improve recognition of meniscal root tears (Figure 2).

Surgical indications

pressure mapping
Representative pressure mapping demonstrates the contact area and pressure distribution in the lateral and medial compartments in a cadaveric left knee specimen at 30° of flexion.

Images: LaPrade RF

MRI of a left knee
MRI of a left knee demonstrates meniscal extrusion (greater than 3 mm) and an edema of the medial femoral condyle on a coronal cut (a). In addition, a sagittal view shows the absence of the posterior horn of the meniscus (“ghost sign”) (b).
posterior root repair of the medial meniscus
This schematic shows a posterior root repair of the medial meniscus of a right knee.

The goal of meniscal root repair is to restore the joint to a near native function of the meniscus and prevent cartilage degradation associated with nonsurgical treatment or meniscectomy. Indications for meniscal root repair are acute, traumatic root tears in patients with nearly normal or normal cartilage (Outerbridge grade 0 to 2) and chronic symptomatic root tears in active patients without significant pre-existing osteoarthritis (OA).

Our preferred repair method utilizes a two-tunnel transtibial pull-out technique. This technique allows for anatomic reduction and fixation of the meniscal root by restoring the joint contact pressure and area similar to the intact state. Of note, drilling tibial tunnels may improve healing of the meniscus-bone interface due to the presence of progenitor cells and growth factors derived from the bone marrow. Chronic tears may be scarred to the capsule and require release of the meniscocapsular junction to allow anatomic repair.

Following root repair, patients are required to remain non-weight-bearing for 6 weeks. Physical therapy should start immediately after surgery and include early passive range of motion from 0° to 90° for the initial 2 weeks and progress to full range of motion thereafter. Progressive weight-bearing begins at 6 weeks, with full weight-bearing at 8 weeks. Deep leg presses and squats greater than 70° of knee flexion should be avoided for at least 4 months after surgery.

Nonsurgical treatment

Nonsurgical treatment is an option for elderly patients, those with significant comorbidities and those with advanced OA (Outerbridge grade 3 or 4 chondromalacia of the ipsilateral compartment).

Symptomatic treatment with rest, ice, NSAIDs and/or an unloader brace may help alleviate symptoms in some cases. If mechanical symptoms are present in this subset of patients, a partial or subtotal meniscectomy may improve symptoms; although, these tears are not usually associated with traditional meniscal-based mechanical symptoms.

Summary

Medial meniscal posterior root tears represent an often unrecognized pathology with potentially devastating long-term effects. Although surgical repair has led to improved patient-reported function, there are conflicting reports on the progression of cartilage degeneration.

A high level of suspicion is required to detect these injuries, and repair is recommended to preserve joint function.

Disclosures: LaPrade reports he is a consultant for and receives royalties from Arthrex, Ossur and Smith & Nephew. Chahla and Geeslin report no relevant financial disclosures.

Proper diagnosis yields higher patient satisfaction after medial meniscal root repair

Medial and lateral menisci are crescent-shaped fibrocartilage structures that provide joint congruity, stabilization and lubrication and act as “shock absorbers” for joint preservation. During weight-bearing activities, the menisci dissipate axial loads and contain hoop stresses. The medial meniscus transmits approximately 50% of the total joint load of the knee medial compartment, thus protecting the articular cartilage from excessive force.

Matthew H. Blake

Matthew H. Blake

Darren L. Johnson

Darren L. Johnson

Tears to the medial meniscal root change the biomechanics and kinematics of the knee, which cause early degeneration of the joint. It has been shown the peak tibiofemoral contact pressure after a total meniscectomy is equal to a posterior medial meniscal root tear.

Recent kinematic/biomechanical studies have also shown the importance of the medial meniscus to anterior translation of the knee. Absence of the medial meniscus (entire medial meniscal root tear) places large stresses on the ACL, the primary ligament that prevents anterior translation of the knee.

Diagnosis

Coronal MRI of posterior medial meniscal root tear
Coronal MRI shows a posterior medial meniscal root tear.
Sagittal MRI shows the “ghost sign
This sagittal MRI shows the “ghost sign."
Axial MRI shows a posterior medial meniscal root tear
Axial MRI shows a posterior medial meniscal root tear.
Posterior medial meniscal root tear
A posterior medial meniscal root tear is shown.
Images: Johnson DL

Making a medial meniscal root tear diagnosis is difficult because the typical history of locking, catching or giving way is less likely to be present. More often, the patient will complain of joint line pain with a minor traumatic event, such as squatting. Likewise, physical exam findings of an effusion, a positive McMurray test and a positive Apley grind test are not usually present.

The most commonly encountered signs are posterior knee pain with deep flexion and joint line tenderness. Another exam finding is palpating the anteromedial joint line, while placing a varus stress on a fully extended knee and feeling for meniscal extrusion. This extrusion should disappear without stress.

Coronal MRI sequences are generally considered the best images for visualization of medial meniscal root tears (Figure 1). While visualization of the meniscal root may be difficult due to MRI slice size, type of MRI and strength of MRI, an extrusion larger than 3 mm highly correlates with a root tear. The “ghost sign” or absence of an identifiable meniscus anterior to the posterior cruciate ligament is also indicative of a root tear (Figure 2). Depending on the cut thickness, axial MRI images may display the root tear (Figure 3).

Treatment

Historically, medial meniscal root tears have been treated conservatively or by partial meniscectomy. With advances in surgical techniques and instrumentation, meniscal root repair is a viable option that can restore the biomechanics and kinematics of the knee (Figure 4). Although a successful outcome of a meniscal root repair is predicated upon appropriate indications for the repair, not all medial meniscal root tears should be repaired.

PAGE BREAK

Medial meniscal root tears are more frequently diagnosed in patients who are older than 40 years, are overweight and cannot recall an inciting event. Radiographs may or may not show medial joint space narrowing. In addition to the root tear, the MRI often shows chondral loss or fissuring, other areas of meniscal tearing, bone marrow edema or osteophyte formation (Figure 5).

We believe these tears are more degenerative in nature, and there is no evidence to support that by repairing these medial meniscal root tears, knee degeneration will be postponed or stopped. It seems that in the above knee, the biology of the medial compartment has gone off the ski slope in a degenerative fashion and reversing that ski slope fall seems to be unproven at this time, particularly in the patient with low functional demands, who is older than 40 years and who has a BMI greater than 30. We have also seen complete meniscal root avulsions in the cruciate ligament-injured knee with complete injury of the medial ligament and posterior oblique ligament that opens in full extension. It is important that these root avulsions are anatomically repaired back to the bone. The anatomic landmark for repair is anterior to the PCL footprint on the tibia.

The ideal candidate for a medial meniscal root repair is an individual younger than 40 years who presents after an acute, traumatic event with a BMI less than 30 and a MRI that shows a medial meniscal root tear without secondary signs of osteoarthrosis or varus malalignment. However, these patients are rare. A case also can be made for medial meniscal root repairs for a symptomatic acute and possibly a chronic medial meniscal root tear in a non-obese patient older than 40 years with a MRI that does not have early arthritic changes. We believe that by repairing these tears, the degenerative process may be delayed or halted (Figure 6).

MRI with abundant subcutaneous fat
A MRI with abundant subcutaneous fat, horizontal meniscal tear, loss of medial compartment articular cartilage, bone marrow edema of femur and tibia is shown (a). A MRI with abundant fat, horizontal medial meniscal tear and medial meniscus root tear is shown (b).
posterior medial meniscal root repair
Shown is a posterior medial meniscal root repair.

The medial meniscus is an important secondary stabilizer of the knee. Knees with a deficient medial meniscus and an ACL tear have an increased anterior tibial translation of about 60% at 90° of flexion. It has been reported that the force experienced by the medial meniscus in the ACL-deficient knee increased by 52% in full extension and by 197% at 60° of flexion under a 134-N load. Reciprocally, an increased force is also placed on an ACL graft with a deficient medial meniscus. As such, it is critical to repair medial meniscal root tears during ACL reconstruction to help stabilize the knee, as well as to decrease stresses that the graft experiences.

Summary

The medial meniscus is an important structure that provides stability, dissipates force and assists to provide normal kinematics of the knee. Tears of the posterior medial meniscal root have shown to disrupt the normal motion of the knee, resulting in degenerative arthritis.

New surgical advances allow surgeons to repair these tears. Successful outcome and patient satisfaction after medial meniscal root repair are established initially upon appropriate diagnosis and patient selection.

Disclosures: Blake and Johnson report no relevant financial disclosures.

PAGE BREAK

Surgical intervention of medial meniscal root tears preserves joint function

Medial meniscal root tears are “radial” tears within 1 cm of the meniscal root insertion or an avulsion of the insertion of the meniscus. These injuries have been reported to change joint loading due to failure of the meniscus to convert axial loads into hoop stresses. This leads to decreased contact area and increased contact pressure and ultimately results in joint overloading and degenerative changes in the knee similar to a total meniscectomy state. This tear pattern was historically unrecognized, although more recently it has been suggested this “hidden” pathology may account for nearly 80% of the total knee replacements in patients younger than 60 years. Biomechanical studies have demonstrated that repair of medial meniscus posterior root tears leads to improved contact mechanics. Studies have also reported that patients who underwent a repair of the posterior root in the medial meniscus slowed the progression of arthritic changes compared with those who had a meniscectomy; although, this did not completely prevent the arthritic changes.

Jorge Chahla

Jorge Chahla

Andrew G. Geeslin

Andrew G. Geeslin

Robert F. LaPrade
Robert F. LaPrade

Posterior medial meniscal root tears are often times degenerative, but these can also occur with multi-ligament knee injuries in the acute setting. In addition, focal chondral lesions occur more commonly with medial than lateral-sided injuries. Non-anatomic placement of a PCL reconstruction tibial tunnel is a reported cause of iatrogenic medial meniscal posterior root tears. Identification of a meniscal root tear on MRI may be challenging due to the relatively small size of the root. However, coronal sections may reveal the presence of meniscal extrusion or vertical defects, and sagittal sections may reveal the “ghost sign” (absence of an identifiable meniscus or increased signal replacing the normal hypointense signal of meniscal tissue). These imaging pearls improve recognition of meniscal root tears (Figure 2).

Surgical indications

pressure mapping
Representative pressure mapping demonstrates the contact area and pressure distribution in the lateral and medial compartments in a cadaveric left knee specimen at 30° of flexion.

Images: LaPrade RF

MRI of a left knee
MRI of a left knee demonstrates meniscal extrusion (greater than 3 mm) and an edema of the medial femoral condyle on a coronal cut (a). In addition, a sagittal view shows the absence of the posterior horn of the meniscus (“ghost sign”) (b).
posterior root repair of the medial meniscus
This schematic shows a posterior root repair of the medial meniscus of a right knee.

The goal of meniscal root repair is to restore the joint to a near native function of the meniscus and prevent cartilage degradation associated with nonsurgical treatment or meniscectomy. Indications for meniscal root repair are acute, traumatic root tears in patients with nearly normal or normal cartilage (Outerbridge grade 0 to 2) and chronic symptomatic root tears in active patients without significant pre-existing osteoarthritis (OA).

Our preferred repair method utilizes a two-tunnel transtibial pull-out technique. This technique allows for anatomic reduction and fixation of the meniscal root by restoring the joint contact pressure and area similar to the intact state. Of note, drilling tibial tunnels may improve healing of the meniscus-bone interface due to the presence of progenitor cells and growth factors derived from the bone marrow. Chronic tears may be scarred to the capsule and require release of the meniscocapsular junction to allow anatomic repair.

Following root repair, patients are required to remain non-weight-bearing for 6 weeks. Physical therapy should start immediately after surgery and include early passive range of motion from 0° to 90° for the initial 2 weeks and progress to full range of motion thereafter. Progressive weight-bearing begins at 6 weeks, with full weight-bearing at 8 weeks. Deep leg presses and squats greater than 70° of knee flexion should be avoided for at least 4 months after surgery.

Nonsurgical treatment

Nonsurgical treatment is an option for elderly patients, those with significant comorbidities and those with advanced OA (Outerbridge grade 3 or 4 chondromalacia of the ipsilateral compartment).

Symptomatic treatment with rest, ice, NSAIDs and/or an unloader brace may help alleviate symptoms in some cases. If mechanical symptoms are present in this subset of patients, a partial or subtotal meniscectomy may improve symptoms; although, these tears are not usually associated with traditional meniscal-based mechanical symptoms.

Summary

Medial meniscal posterior root tears represent an often unrecognized pathology with potentially devastating long-term effects. Although surgical repair has led to improved patient-reported function, there are conflicting reports on the progression of cartilage degeneration.

A high level of suspicion is required to detect these injuries, and repair is recommended to preserve joint function.

Disclosures: LaPrade reports he is a consultant for and receives royalties from Arthrex, Ossur and Smith & Nephew. Chahla and Geeslin report no relevant financial disclosures.