The lateral collateral ligament (LCL) is a one of the four major ligaments in the knee. The LCL is on the outside of the knee connecting the thighbone (femur) to the smaller bone in the lower leg (fibular). Its main function is to avoid varus stress across the knee (where the knee buckles outwards). Together with the popliteofibular ligament, the capsule of the joint and the popliteus tendon, it forms the PLC Complex which provides external rotational stability.
Injuries to the LCL and posterior lateral corner result from a rotational force across the knee often with buckling of the knee. A contact injury, such as a direct blow to the medial side (inside of knee), or a noncontact injury, such as a hyperextension stress. It is also commonly associated with an ACL tear which occurs with a high level of force and sports injury.
- Feeling that the knee may give way under stress and isn’t stable
- Pain that can be mild or acute
- Swelling and tenderness along the outside of the knee
- A locking or catching in the joint when it is moved
- Numbness or weakness in the foot may occur if the peroneal nerve, which is near the ligament is stretched during the injury or is pressed by swelling in surrounding tissues