LCL Tear

The lateral collateral ligament (LCL) is a thin band that runs along the outside of the knee and connects the thighbone (femur) to the fibula, which is the small bone that runs down the side of the knee and connects to the ankle. Similar to the medial collateral ligament (MCL), the LCL's primary function is to stabilize the knee as it moves. Tears to the LCL commonly occur as a result of direct blows to the inside of the knee, which can over-stretch the ligaments on the outside of the knee and, in some cases, cause them to tear.

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The tear can occur in the middle or at either end of the ligament. LCL tears often occur while playing sports in which there are violent collisions (such as football or hockey). It is important to note that an LCL tear rarely occurs in isolation — it usually is in conjunction with another knee injury.

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The most common symptoms of an LCL tear are pain, stiffness, swelling and tenderness along the outside part of the knee. Your knee may feel loose, as though it will give way under stress, or it may lock. More severe tears can cause numbness or weakness in the foot, which occurs in the peroneal nerve (located near the LCL) if it is stretched at the time of injury or squeezed by swelling of the surrounding tissues.

Your doctor will check for pain or tenderness along the inside of the knee. In order to determine the severity of the injury, he or she will apply pressure to the outside of your knee while your leg is both bent and straight.

In some cases, the immediate pain and swelling may make it too difficult for your doctor to accurately gauge the severity of the injury. If this occurs, you may be asked to wear a light splint and ice and elevate your knee until the swelling and pain lessen, so that an accurate diagnosis can be made.

In addition, your doctor may order the following tests:

  • X-ray: These are usually ordered to evaluate the bones and alignment around the knee.
  • Magnetic Resonance Imaging (MRI): This test is more than 90 percent accurate in assessing the severity of LCL injuries, and it is commonly used if the physical examination does not yield a satisfactory diagnosis.

If the torn ligament does not heal sufficiently, you may experience instability in the joint, making it more susceptible to re-injury. Although more-severe injuries often require surgery, lesser damage to the LCL usually responds very well to non-surgical treatment. Recovery time depends on the severity of the injury.

Rehabilitation for an LCL tear consists of:

  • A period of rest
  • Bracing
  • Physical therapy

Once pain and swelling have subsided, you should be able to begin exercises to restore strength and normal range of motion to your knee.

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Reviewed by health care specialists at UCSF Medical Center.

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