Medial (MCL) and Lateral (LCL) Collateral Ligament Tears: Overview

Medial (MCL) and Lateral (LCL) Collateral Ligament Tears: Overview

The knee is a complex joint that requires support from many stabilizing ligaments. Ligaments are made of strong, thick, rope-like fibers that connect bone to bone.

The collateral ligaments are located on the outside of the knee joint and include the medial collateral ligament, or MCL, and the lateral collateral ligament, or LCL. The MCL is located on the inner side of the knee and connects the thigh bone, or femur, to the shin bone, or tibia. The LCL is located on the outer side of the knee and connects the thigh bone to the fibula, the small bone on the outer side of the lower leg. Together, these ligaments stabilize the knee joint against side-to-side motion.

There are different ways that these ligaments can be injured. Often, injuries to the collateral ligaments result from quick twisting or pivoting motions when the foot is planted. These types of injuries stretch the collateral ligaments more than normal and can damage or tear the ligament fibers. Injuries also frequently occur with contact sports that involve a direct blow to the knee when the foot is planted.

The LCL gets injured when a force is applied to the inner side of the knee, causing the LCL on the outer side of the knee to overstretch. LCL injuries typically happen in conjunction with damage to other structures in the knee, which result from a high-velocity, high-energy trauma. This may include a fall from heights, a car or motorcycle accident, or a major sports injury.

The MCL is commonly injured when a force is applied to the outer side of the knee, causing the MCL on the inner side of the knee to overstretch. Injury to the MCL is more common, making up an estimated 60% of all knee injuries. It is common for injuries to the collateral ligaments to also affect other ligaments that support the knee.

Patients will typically experience pain and swelling either at the inner side of the knee with an MCL tear or at the outer side of the knee with an LCL tear. The knee may also feel unstable to diagnose collateral ligament tears. A healthcare provider will ask a patient about their symptoms and examine the knee. A healthcare provider may apply a force to the inner and outer sides of the knee to see if either of the ligaments are loose or painful.

Imaging methods like x-rays or MRIs may also be used to diagnose a collateral ligament tear. X-rays are typically taken with the knee bent at 20 degrees to examine the space within the knee joint. More space on one side of the knee means that the ligament is damaged and unable to properly stabilize that side of the knee joint. An MRI will give a better image of the knee ligaments and can help determine the grade of a tear, with grade 1 being mild, microscopic tears; grade 2 being moderate, partial tears; and grade 3 being severe, complete tears. Proper diagnosis from a healthcare provider will help determine the best course of treatment for recovery from a collateral ligament tear.