Your knee ligaments connect your thighbone to your lower leg bones. The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are found on the sides of your knee. Three bones meet to form your knee joint: your thighbone (femur), shinbone (tibia), and kneecap (patella). Your kneecap sits in front of the joint to provide some protection. Because the knee joint relies just on these ligaments and surrounding muscles for stability, it is easily injured. Any direct contact to the knee or hard muscle contraction — such as changing direction rapidly while running — can injure a knee ligament.
Causes and risk factors
Knee ligament sprains or tears are a common sports injury. Athletes who participate in direct contact sports like football or soccer are more likely to injure their collateral ligaments. The MCL is injured more often than the LCL. Due to the more complex anatomy of the outside of the knee, if you injure your LCL, you usually injure other structures in the joint, as well.
- Pain at the sides of your knee. If there is an MCL injury, the pain is on the inside of the knee; an LCL injury may cause pain on the outside of the knee.
- Swelling over the site of the injury.
- Instability — the feeling that your knee is giving way.
Diagnosis and treatment
Injuries to the MCL rarely require surgery. If you have injured just your LCL, treatment is similar to an MCL sprain. But if your LCL injury involves other structures in your knee, your treatment will address those, as well.
Ice. Icing your injury is important in the healing process. The proper way to ice an injury is to use crushed ice directly to the injured area for 15 to 20 minutes at a time, with at least 1 hour between icing sessions. Chemical cold products (“blue” ice) should not be placed directly on the skin and are not as effective.
Bracing. Your knee must be protected from the same sideways force that caused the injury. You may need to change your daily activities to avoid risky movements. Your doctor may recommend a brace to protect the injured ligament from stress. To further protect your knee, you may be given crutches to keep you from putting weight on your leg.
Physical therapy. Your doctor may suggest strengthening exercises. Specific exercises will restore function to your knee and strengthen the leg muscles that support it.
If the collateral ligament is torn in such a way that it cannot heal or is associated with other ligament injuries, your doctor may suggest surgery to repair it.