Lateral collateral ligament (LCL) injury is a stretch, partial tear, or complete tear of the ligament on the outside of the knee.

The lateral collateral ligament (LCL) extends from the top outside surface of the fibula (the bone on the outside of the lower leg) to the bottom outside surface of the thigh bone. The ligament holds the knee on the outside of the joint.

The LCL is usually injured by pressure placed on the knee joint from the inside, which results in stress on the outside of the joint.

• Knee instability
• Knee pain or tenderness along the outside of the knee
• Knee swelling

A lateral collateral ligament test may reveal looseness in the ligament. This involves bending the knee to 25 degrees and placing pressure on the inside surface of the knee.

Other tests may include:

• Knee MRI
• Knee joint x-rays

Treatment includes applying ice to the area, raising the knee above heart level, and nonsteroidal anti-inflammatory drugs (NSAIDS). You should limit physical activity until the pain and swelling go away.

After an initial period of keeping the knee still (usually with a knee brace), knee strengthening and stretching exercises should be done. Physical therapy may be helpful to help regain knee and leg strength.

Surgery for isolated LCL injuries is not generally necessary. However, this ligament is commonly injured during significant trauma, including knee dislocations. When injuries to the LCL occur with other ligament injuries, surgical repair is needed to prevent future instability of the knee.

Call your health care provider if you injure your knee and symptoms of LCL injury occur.

Call your health care provider if you are being treated for an LCL injury and you notice increased instability in your knee, if pain or swelling return after they initially subsided, or if your injury does not go away with time.

Also call if you reinjure your knee.

Use proper technique when exercising or playing sports. Many cases may not be preventable.