The lateral collateral ligament (LCL) is located on the lateral aspect of the knee, and thus belongs to a complex of structures collectively known as the posterolateral corner of the knee. Other structures of the posterolateral corner include the popliteofibular ligament, the popliteus ligament, the arcuate ligament, the short lateral ligament, and the posterolateral joint capsule.
The LCL connects the femur to the fibula. It attaches on the femur just proximal and posterior to the femoral lateral epicondyle and extends approximately 70 mm down the knee to attach to the fibular head.
Rounded, more narrow, and less broad than the medial collateral ligament (MCL), the LCL stretches obliquely downward and backward from the lateral epicondyle of the femur above, to the head of the fibula below. In contrast to the MCL, it is fused with neither the capsular ligament nor the lateral meniscus. Because of this, the lateral collateral ligament is more flexible than its medial fellow, and is therefore less susceptible to injury.
From 0 to 30 degrees of knee flexion, the LCL is the main structure preventing varus angulation of the knee joint. The LCL and MCL are taut when the knee joint is in extension. With the knee in flexion, the radius of curvatures of the condyles is decreased and the origin and insertions of the ligaments are brought closer together which make them lax. Together, the LCL and the MCL stabilize the knee joint in the coronal plane.
Disability if injured
Most patients continue to ambulate after an LCL injury. They generally have pain localized the lateral aspect of the knee; swelling and erythema may be present. Instability is not typical with grade I and II injuries. Rotational instability is common with grade III injuries.
As with an MCL injury, treatment of a grade I or grade II LCL injury is usually conservative. The first choice for treatment should be physical therapy, which includes measures to control inflammation as well as bracing. More severe grade III injuries generally require surgery because they usually involve the posterolateral corner of the knee. Following surgery, these patients need physical therapy, including bracing, for approximately 3 months to reduce the risk of later instability.