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The collateral ligaments are located on the inner and outer sides of the knee joint. They serve to stabilize and guide the knee joint through various ranges of motion.

Image by kevin turcios

The knee joint's collateral ligaments are a group of ligaments that stabilize the knee joint and prevent excessive lateral movement. There are two collateral ligaments in the knee joint: the medial collateral ligament (MCL) and the lateral collateral ligament (LCL).

The MCL is located on the inner side of the knee and connects the thigh bone to the shinbone. It is primarily responsible for protecting the knee against valgus forces, which push the knee outward. The LCL is located on the outer side of the knee and connects the thigh bone to the fibula. It is mainly responsible for protecting the knee against varus forces, which push the knee inward.

Knee joint instability can be caused by collateral ligament damage. Collateral ligament injuries can result from sudden movements or knee injuries, such as a sprain or overstretching. A common cause of collateral ligament injuries is sports-related injuries, especially in contact sports like soccer or rugby.


The diagnosis of a collateral ligament injury is typically made through a physical examination and imaging studies such as X-rays, MRI, or CT scans. A collateral ligament injury can be classified into three grades of severity, with Grade 1 representing mild stretching of the ligament and Grade 3 indicating a complete tear of the ligament.


The treatment of collateral ligament injuries depends on the severity of the injury. Mild stretching of the ligament can often be treated with conservative measures such as knee immobilization, pain medication, and physical therapy. A complete tear of the ligament usually requires surgery to repair the ligament or stabilize it with a knee brace.

It is important to diagnose and treat collateral ligament injuries early to avoid long-term instability and complications such as arthritis. Careful rehabilitation after a collateral ligament injury is crucial to restore full mobility and strength of the knee joint.

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