Description of an LCL Injury (FCL Injury)
The lateral collateral ligament (LCL), also called the fibular collateral ligament (FCL), is the main structure on the lateral, or outside, portion of the knee to prevent the knee from gapping open. The term fibular collateral ligament (FCL) is more anatomically correct, but this ligament is more commonly referred to as lateral collateral ligament (LCL). In clinical terms, this is noted as varus gapping. It is a thin, round, stout ligament, which courses from the femur down to the lateral aspect of the fibular head.
An LCL injury can occur with sudden stops and starts, a blow to the inside of their knee, or a contact or noncontact hyperextension injury. Sometimes a LCL tear of the knee can go undiagnosed for a few weeks before an athlete notices problems with instability.
Symptoms of an LCL Injury (FCL Injury)
- Mild swelling and pain – no obvious deep swelling within the knee
- Difficulty stopping and cutting
- Instability of the knee shifting side-to-side
Many athletes note that they cannot stop and cut towards the side where they have the LCL tear, due to a feeling of instability of the knee shifting side-to-side. Unfortunately, due to the unstable nature of the lateral compartment of the knee with two convex surfaces opposing each other, grade III lateral collateral ligament tears usually do not heal, and can lead to further instability.
The diagnosis of an LCL tear is made through a combination of physical examination and radiographic techniques. In most circumstances, the athletes will complain of a feeling of side-to-side instability and have varus gapping on the physical exam. Varus stress x-rays are very useful to determine the amount of gapping to determine if it is a complete or partial tear and are highly recommended to be performed. Studies have reported that greater than 2.7 millimeters of side-to-side gapping is consistent with a complete tear of the lateral (fibular) collateral ligament and a reconstruction should be considered.