The fibular collateral ligament (FCL), also known as the lateral collateral ligament (LCL), is one of the four primary stabilizing ligaments of the knee. It is essential in providing lateral stability to the knee joint.
Location
The FCL is located on the outer (lateral) aspect of the knee. It attaches proximally to the lateral femoral condyle and distally to the head of the fibula.
Structure
Morphology: The FCL is a cord-like, round ligament, distinctly separate from the joint capsule and the lateral meniscus.
Composition: Like other ligaments, the FCL consists of dense connective tissue, which is both resilient and slightly flexible to withstand tensile stresses.
Function
- Lateral Stability: Its primary function is to stabilize the knee against varus forces (forces pushing the knee inward). This is vital during side-to-side movements and when landing from jumps.
- Rotational Stability: The FCL also helps resist excessive external rotation of the tibia.
Clinical Significance
The fibular collateral ligament (FCL), also known as the lateral collateral ligament (LCL), holds notable clinical significance as a primary stabilizer against varus and external rotational forces on the knee. Injuries to the FCL can compromise the knee’s lateral stability, potentially leading to pain, swelling, and a feeling of the knee “giving way” during certain activities.
Although FCL tears are less common than medial collateral ligament (MCL) injuries due to the protective overlay of the iliotibial band and other structures, when they do occur, they often result from direct trauma or a significant varus force to the knee. Importantly, isolated FCL injuries are rare; they frequently present in combination with other ligamentous injuries, particularly to the cruciate ligaments. This complexity underscores the need for a comprehensive clinical and imaging evaluation to rule out concurrent damage.
Timely and accurate diagnosis followed by appropriate treatment, whether conservative or surgical, is essential to restore optimal knee function and prevent long-term complications, including osteoarthritis and chronic instability.
