Ligaments are dense strands of tissue that link two bones together across a joint. There are 4 main ligaments that span the knee joint: Lateral Collateral Ligament (LCL), Medial Collateral Ligament (MCL), Posterior Cruciate Ligament (PCL) and Anterior Cruciate Ligament (ACL). Ligament tears rarely occur in isolation and many patients will have a concomitant bone bruise or cartilage tear. LCL and PCL tears are unusual injuries and commonly occur as a result of high energy injuries like car accidents causing a knee dislocation. Medial Collateral and Anterior Cruciate ligament injuries are more common and discussed individually below.
Medial Collateral ligament (MCL) tears manifest in sharp pain on the inside (medial) aspect of the knee after a hit from the lateral (outside) aspect of the knee. Some patients complain of a feeling of instability when putting weight on the leg. Ligament tears are graded on the severity of the ligament damage from 1-3, with a grade 3 sprain regarded as a complete rupture of the ligament. An MRI of the knee is necessary to make sure there are no associated soft tissue injuries. Meniscus tears occur in conjunction with MCL tears. For isolated MCL tears, surgery is not needed and most patients are treated with a hinged knee brace and gradual rehabilitation with physical therapy. Pain associated with the tear is stubborn and persists for several months after the injury.
Anterior Cruciate ligament (ACL) tears commonly occur in conjunction with pivoting sports (basketball, football, skiing) and are much more common in female athletes. Patients may describe a history of a pop in the knee and most have a large effusion (accumulation of fluid inside the joint). Most are able to stand and walk within a few days but many describe feeling a shifting or loosening of the knee joint, especially when changing direction. The diagnosis is confirmed by MRI scan which will usually show the ligament tear clearly. Initial management will consist of physical therapy to help regain motion in the knee with special focus on regaining the quadriceps strength that diminishes rapidly after the injury. Surgery to reconstruct the ligament is often needed to restore stability to the knee but many patients choose not to undergo surgical reconstruction and can be effectively managed with brace wear. Reconstruction of the injured ligament is done with either a cadaver tendon (allograft) or one of the patient’s own tendons (autograft). Full recovery and return to sporting activity usually takes 6-9 months but most patients are independently mobile within 4 weeks