summary A medial collateral ligament (MCL) knee injury is a traumatic knee injury that typically occurs as a result of a sudden valgus force to the lateral aspect of the knee. Diagnosis can be suspected with increased valgus laxity on physical exam but requires MRI for confirmation. Treatment is generally nonoperative with bracing. Surgical management may be indicated for high grade injuries in the setting of persistent valgus instability. Epidemiology Incidence most common ligamentous injury of the knee 40% of knee ligament injuries incidence is likely higher than reported low grade injuries can be missed Demographics males > females commonly occur in athletes account of 8% of all athletic knee injuries highest risk in skiing, rugby, football, soccer and ice hockey Etiology Pathophysiology valgus stress is the most common mechanism of injury usually with the knee held in slight flexion and external rotation contact injury more common than noncontact direct blow to the lateral knee with valgus force more often result in high grade / complete ligament disruption than noncontact injury rupture usually occurs at the femoral insertion of the MCL proximal MCL tears have greater healing rates distal MCL tears have inferior healing and residual valgus laxity noncontact injury less common than contact but more common in skiing pivoting or cutting activities with valgus and external rotation force more often result in low grade / incomplete ligament injury Associated conditions anterior cruciate ligament (ACL) tear most common associated injury make up ~95% of injuries associated with nonisolated MCL injury combined ACL-MCL is the most common multiligamentous knee injury presence of hemarthrosis is highly suggestive often associated with high grade MCL injuries grade III > grade II > grade I meniscus tear medial > lateral up to 5% of isolated MCL injuries are associated with meniscus tears Pellegrini-Stieda syndrome calcification at the medial femoral insertion site results from chronic MCL deficiency Anatomy Ligaments of the knee Anatomy superficial MCL located in layer II of the medial knee with posteromedial corner ligaments and medial patellofemoral ligament femoral attachment medial epicondyle 1cm anterior and distal to the adductor tubercle tibial attachment proximal tibia periosteum 4.5cm distal to the joint line deep and posterior to the pes anserinus deep MCL located in layer III of the medial knee with the joint capsule composed of meniscofemoral and meniscotibial ligaments Vascular supply superior medial and inferior medial geniculate arteries Function superficial MCL primary stabilizer to valgus stress at all angles of knee flexion greatest stability contribution at 25 degrees knee flexion (78%) secondary stabilizer to tibial external rotation and anterior/posterior tibial translation deep MCL secondary stabilizer to valgus stress greatest stability contribution at full knee extension other stabilizers of the medial knee static stabilizers posterior oblique ligament resists tibial internal rotation at full knee extension secondary restraint to valgus stress oblique popliteal ligament posterior capsule dynamic stabilizers semimembranosus complex consists of 5 attachments vastus medialis medial retinaculum pes anserine muscle group sartorius semitendinosus gracilis Classification American Medical Association (AMA) Classification Based on joint laxity alone (described in 1966) Valgus stress applied with the knee in 30 degrees of flexion Graded by the amount of medial joint line opening < 3 mm considered physiologic laxity Caused confusion and difficulty comparing treatment results Grade I 3-5 mm Grade II 6-10 mm Grade III > 10 mm Hughston Modification of the AMA Classification Based on joint laxity and injury severity. Severity graded by the extent of tenderness and quality of the endpoint with valgus stress at 30. Degrees of knee flexion. Often referred to as "degree" of injury. Grade I Mild First-degree injury Firm endpoint with no joint laxity Stretch injury or few MCL fibers torn (no significant loss of ligament integrity) Grade II Moderate Second-degree injury Incomplete / partial MCL tear Firm endpoint +/- mild increase in joint laxity Some MCL fibers remain intact, generating the firm endpoint Grade III Severe Third-degree injury Complete MCL tear No endpoint with valgus stress Increased joint laxity (subdivided by degree of joint laxity) Grade 1+: 3-5 mm Grade 2+: 6-10 mm Grade 3+: > 10 mm Presentation History "pop" reported at time of injury Symptoms medial joint line pain difficulty ambulating due to pain or instability Physical exam inspection and palpation tenderness along medial aspect of knee ecchymosis knee effusion ROM and stability valgus stress testing at 30° knee flexion isolates the superficial MCL medial gapping as compared to opposite knee indicates grade of injury 1- 4 mm = grade I 5-9 mm = grade II > or equal to 10 mm = grade III valgus stressing at 0° knee extension medial laxity with valgus stress indicates posteromedial capsule or cruciate ligament injury neurovascular exam saphenous nerve exam evaluate for additional injuries ACL PCL patellar dislocation medial meniscal tear Imaging Radiographs recommended AP and lateral optional view stress radiographs in skeletally immature patient may indicate gapping through physeal fracture findings usually normal calcification at the medial femoral insertion site (Pellegrini-Stieda Syndrome) MRI modality of choice for MCL injuries identifies location and extent of injury useful for evaluating other injuries Treatment Nonoperative NSAIDs, rest, therapy indications grade I therapy quad sets, SLRs, and hip adduction above the knee to begin immediately cycling and progressive resistance exercises as tolerated return to play grade I may return to play at 5-7 days bracing, NSAIDs, rest, therapy indications grades II grade III if stable to valgus stress in full extension no associated cruciate injury technique immobilizer for comfort hinged knee brace for ambulation return to play grade II return to play at 2-4 weeks grade III return to play at 4-8 weeks outcomes distal MCL injuries have less healing potential than proximal injuries Operative ligament repair vs. reconstruction relative indications acute repair in grade III injuries in the setting of multi-ligament knee injury displaced distal avulsions with "stener-type" lesion entrapment of the torn end in the medial compartment sub-acute repair in grade III injuries continued instability despite nonoperative treatment >10 mm medial sided opening in full extension reconstruction chronic injury loss of adequate tissue for repair technique diagnostic arthroscopy recommended for all surgical candidates to rule out associated injuries Prevention knee bracing functional bracing may reduce MCL injury in football players, particularly interior linemen Techniques MCL repair approach medial approach to the knee indications acute injuries techniques ligament avulsions should be reattached with suture anchors in 30 degrees of flexion interstitial disruption anterior advancement of the MCL to femoral and tibial origins internal brace MCL reconstruction approach medial approach to the knee indications chronic instability insufficient tissue for repair graft type can use semitendinosus autograft or hamstring, tibialis anterior or Achilles tendon allograft Complications Loss of motion Neurological injury saphenous nerve Laxity associated with distal MCL injuries