Injury of Knee Ligaments

Abstract

The anterior cruciate ligament (ACL) is an intra-articular but extra-synovial ligament that is the primary restraint to anterior tibial translation and secondary restraint to tibial rotation. At least two-thirds of ACL tears occur during noncontact injuries. ACL rupture may be isolated, or concurrent lesion to medial collateral ligament (MCL) and the capsule and/or to lateral collateral ligament (LCL) and posterolateral corner may occur. At the time of injury, the athlete hears a “pop” and feels pain, and giving way symptom, and although may be able to walk off the field however shows inability to continue the activity. The injury is accompanied by swelling due to hemarthrosis. ACL rupture is functionally disabling and predisposes to subsequent injuries of the menisci and cartilage and early onset of osteoarthritis. The level of activity of the patient, the desire to return to the pre-injury level, and the recurrent giving way symptoms indicate operative treatment plan that consists of arthroscopic ACL reconstruction. Medial collateral ligament provides 78% of the valgus restraining force of the knee. MCL injury is common during contact sports and may result from contact or noncontact valgus stress. It presents as an isolated injury or commonly in combination with injury to the ACL, posterior cruciate ligament (PCL), or both. Isolated MCL tear leads to valgus laxity in flexion indicated by valgus stress test at 30° of flexion, while additional injury to the secondary valgus restraints (posteromedial capsule or ACL) leads to increased laxity and positive valgus stress testing at extension. Acute isolated MCL injury is treated with nonoperative management except from the case of bony avulsions where acute repair may be indicated. Combined MCL and cruciate ligament injuries are treated with a nonoperative management of the MCL with the delayed treatment of the ACL once the MCL is healed. Chronic MCL injuries that lead to inability to participate in athletic activities are treated via operative reconstruction. The PCL accounts for about 95% of the total restrain to posterior translation of the tibia in regard to the femur. It can be injured from a posteriorly directed force on the upper front of flexed knee, fall on a flexed knee, and knee hyperflexion or hyperextension. Isolated PCL injury may occur or combination with posterolateral corner (PLC) injury resulting in posterolateral rotatory instability (PLRI). Nonoperative management is proposed for acute grade I–II isolated PCL injuries, while surgery is recommended in patients with grade III injuries, symptomatic grade II injuries, chronic symptomatic isolated PCL lesions, and multi-ligament injuries. The LCL is the primary static restraint to varus opening of the knee. The posterior lateral corner (PLC) of the knee consists of various anatomic structures with primary function to resist varus rotation, external tibial rotation, and posterior tibial translation, and its injury results in posterolateral rotatory instability (PLRI). The LCL is most commonly injured in combination with one of the cruciate ligaments. PLC injuries are often accompanied by other ligamentous injuries, especially PCL injury. Grade III LCL injuries are treated surgically. For acute injuries of the posterolateral structures, PLRI surgical treatment within 2 weeks is widely recommended before significant capsular scarring occurs.