Ligaments are strong, dense structures made of connective tissue that stabilize a joint. They connect bone to bone across the joint. The knee joint is located where the end of the thigh bone (femur) meets the top of the shin bone (tibia) and four main ligaments connect these two bones:
- Medial collateral ligament (MCL) runs along the inside of the knee. It prevents the knee from bending in.
- Lateral collateral ligament (LCL) runs along the outside of the knee. It prevents the knee from bending out.
- Anterior cruciate ligament (ACL) is in the middle of the knee. It prevents the shin bone from sliding out in front of the thigh bone.
- Posterior cruciate ligament (PCL) works with the ACL. It prevents the shin bone from sliding backwards under the femur.
The MCL’s primary function is to prevent the leg from over-extending inward, but it also is part of the mechanism that stabilizes the knee and allows it to rotate.
Injuries to the MCL commonly occur as a result of a strong force hitting the outside of the knee that causes the MCL — and, possibly, other ligaments on the inside of the knee, such as the anterior cruciate ligament (ACL) — to stretch or tear.
This can happen while playing sports where one player collides with another player from the side. In addition, MCL tears occur in sports where there are a lot of quick stops and turns, such as soccer, basketball and skiing. Slipping on ice, if the lower leg splays out, also can produce the same result.
Another cause of injury is repeated stress, where the MCL loses its normal elasticity and becomes limp, like a worn-out rubber band.
Signs & Symptoms
Initial symptoms of an MCL tear include:
- Pain or tenderness
Symptoms occur along the inner side of the knee. (The MCL is located on the side of the knee adjacent to the other knee.) Depending on the severity of the injury, pain can range from mild to severe.
In addition, the knee may feel unsteady, or may lock or “catch.”
The doctor will check for pain or tenderness along the inside of the knee. In addition, he or she will approximate the cause of the injury by exerting pressure on the outside of the knee while the leg is both bent and straight.
Depending on the degree of pain or looseness of the knee joint, the injury will be classified as one of three grades:
- Grade 1 – There is some tenderness and minor pain at the point of the injury.
- Grade 2 – There is noticeable looseness in the knee (“opening up” approximately five millimeters) when manipulated by hand, major pain and tenderness at the inside of the knee, and in some cases swelling.
- Grade 3 – There is considerable pain and tenderness at the inside of the knee along with some swelling and marked joint instability (the knee opens up approximately one centimeter when manipulated). A grade three MCL tear often occurs in conjunction with an ACL tear or, more rarely, with a PCL tear.
In some cases, the immediate pain and swelling may make it too difficult for the doctor to accurately gauge the severity of the injury. If this occurs, the patient may be asked to wear a light splint and ice and elevate the knee until the swelling and pain lessen, so that an accurate diagnosis can be made.
In addition, the following tests may be ordered:
- X-ray – To assess for other damage and bone injury
- Magnetic Resonance Imaging (MRI) – This test is 90 percent accurate in diagnosing MCL injuries and may be ordered if the physical examination is unclear or if other injuries are suspected.
- Stress X-ray – This also may be used to look for ligament tears. Although this test is similar to a normal X-ray, the doctor or technician will hold the knee open from the side so that any widening of the joint space will be evident on the X-ray.
On average, it takes six weeks for a MCL injury to heal. The initial treatment for most Grade 1, 2 or 3 MCL tears focuses on reducing the pain and inflammation in the knee while immobilizing the knee to keep it stabilized. This includes:
- Resting, icing and elevating the knee
- Taking pain relievers, such as aspirin and ibuprofen, to ease pain and swelling
- Wearing a lightweight cast or brace that allows the knee to move backward and forward while restricting side-to-side movement. It usually is recommended to keep the knee immobilized like this for 72 hours, depending on the severity of the injury.
The cast or brace may be designed so that the knee cannot be bent at all. In this case, the leg should be kept elevated even when sitting in a chair, to reduce blood flow to the knee.
Once the pain and swelling subside, rehabilitation begins, which will include exercises to restore strength and normal range of motion to the knee. If the knee feels sore while doing these exercises, the patient should proceed slowly to prevent further irritation.
If the torn ligament does not heal sufficiently, instability in the joint may be experienced, and the knee will be more susceptible to re-injury. The MCL usually responds very well to non-surgical treatment, although surgery may be required in rare cases. Depending on the severity of the injury, a period of rest, bracing and physical therapy usually is sufficient to heal the tear.
Once the MCL has healed fully, the patient should have a minimum of long-term effects, providing there was no other damage to the knee.
Recovery times differ depending on the severity of the injury:
- A minor, or Grade 1, MCL tear can take from a few days to a week and a half to heal sufficiently for patient to return to normal activities, including sports.
- A Grade 2 tear can take from two to four weeks to heal.
- A Grade 3 tear usually takes from four to eight weeks to heal, unless it is associated with damage to the ACL, in which case the recovery time may be longer.