The lateral collateral ligament is a thin band of tissue along the outer side of the knee. It joins the thighbone (femur) to the fibula. (The fibula is the small bone of the lower leg that runs down the side of the knee to the ankle.) Like the medial collateral ligament, the lateral collateral ligament's main job is to keep the knee stable as it moves.
Tears to the lateral collateral ligament most often occur from a direct blow to the inside of the knee. This can stretch the ligaments on the outside of the near too far and may cause them to tear. This type of injury occurs in sports that require a lot of quick stops and turns such as soccer, basketball and skiing or ones where there are violent collisions such as football or hockey.
The ligament can also be injured by repeated stress that causes it to lose its normal elasticity. Most knee injuries are to the ligaments that support the knee, not the knee joint itself.
Symptoms of a Torn Lateral Collateral Ligament
Signs of a torn lateral collateral ligament include:
- A feeling that the knee may give way and isn't stable
- A locking or catching in the joint when moved
- Numbness or weakness in the foot. This may occur if the nearby peroneal nerve is stretched during the injury or is pressed by swelling in around it
- Swelling and tenderness along the outside of the knee
Diagnosing a Torn Lateral Collateral Ligament
Typically, your doctor will ask you how the injury occurred, how your knee has been feeling since the injury and whether you have had other knee injuries. You may be asked about your physical and athletic goals to help your doctor decide on the best treatment for you.
Your injury will be classified as follows:
- Grade 1 ligament tear: Some tenderness and minor pain at the point of the injury. This means there have been small tears in the ligament.
- Grade 2 ligament tear: Noticeable looseness in the knee (the knee opens up about five millimeters) when moved by hand. There is major pain and tenderness on the inner side of the knee as well as swelling. This means there have been larger tears in the ligament. The ligament is not torn in two, however.
- Grade 3 ligament tear: Considerable pain and tenderness at the inner side of the knee; some swelling and marked joint instability. The knee opens up slightly less than half an inch when moved. A grade 3 LCL tear means the ligament is completely torn. There may also be a tear of the anterior cruciate ligament.
If there is too much pain and swelling to accurately judge how serious the injury is, your doctor may recommend that you wear a light splint, apply ice and raise your knee. Once the swelling and pain have gone down somewhat, he or she can then make the diagnosis.
Your doctor may order a magnetic resonance imaging (MRI) scan. An MRI has an accuracy rate of nearly 90% in determining whether and how badly a lateral collateral ligament has been torn. It is not very good, however, at detailing a partial tear.
Non-surgical Treatment of Lateral Collateral Ligament Tears
Lateral collateral ligament tears do not heal quite as well as medial collateral ligament tears do. Grade 3 lateral collateral ligament tears may require surgery.
In some cases, all that is required to complete the healing process is rest, wearing a brace, taking pain relievers such as ibuprofen and having physical therapy. Your doctor may recommend that you wear a lightweight cast or brace that allows your knee to move backward and forward but restricts side-to-side movement. This is usually worn 72 hours. Depending on how well it reduces your pain and swelling, you may be able to start a rehabilitative program in a few days.
When the pain and swelling have gone down, you should be able to start exercises to restore strength and normal range of motion to your knee. If you are still have soreness while doing these exercises, proceed slowly to prevent further irritation. It may take anywhere from one to eight weeks to fully recover, depending on the grade of your injury.
Surgical Treatment for Lateral Collateral Ligament Tears
If the lateral collateral ligament was torn where it attaches to the thighbone (femur) or shinbone (tibia), the surgeon will re-attach the ligament to the bone using large stitches or a metal bone staple.
If the tear happened in the middle of the ligament, the surgeon will sew the torn ends together.
If the damage was severe and cannot be repaired, your surgeon may reconstruct a tendon by using a graft taken from a tendon of your thigh muscles (quadriceps) or your hamstrings.
Lateral knee reconstruction is an open-knee procedure, and is not done arthroscopically. The tendon graft is passed through bone tunnels and fixed to the thighbone and lower leg bone (fibula) using screws or posts or with stitches tied around a post.