What does the lateral collateral ligament (LCL) prevent?

The lateral collateral ligament (LCL) plays a critical role in stabilizing the knee joint, specifically by preventing excessive varus displacement of the tibia. Varus displacement occurs when the knee is positioned such that the lower leg (tibia) moves inward relative to the upper leg (femur), creating an angle that is sharper on the lateral side of the knee. This inward displacement can lead to instability and potential injury to the structures surrounding the knee.

The LCL, located on the outside of the knee, is responsible for resisting this varus stress, thereby helping to maintain proper alignment and stability during movements that involve lateral forces. By controlling the movement of the tibia in relation to the femur, the LCL protects the integrity of the knee joint, allowing for normal functional mobility without undue strain on the ligaments and cartilage.

Understanding the role of the LCL in preventing varus displacement is essential for physical therapists, particularly in assessing knee stability and designing rehabilitation protocols for patients with knee injuries.