Ligament tear at the knee

The knee joint is heavily stressed by various movements, such as during sports activities. For this reason, the knee is stabilized and supported by the lateral and cruciate ligaments, as well as by the muscles of the lower and upper thigh.

The collateral ligaments are responsible for stabilizing the inside and outside of the knee, especially when the knee is in an extended position. When the knee joint is bent, the collateral ligaments are not taut. In contrast, the anterior cruciate ligament is responsible for stabilizing the knee when it is strained forward and the posterior cruciate ligament is responsible for stabilizing the knee when it is strained backward.

In most cases, the anterior cruciate ligament is affected by accidents, but the medial collateral ligament can also often be damaged, especially by various sports injuries (skiing, football).

An injury to the medial collateral ligament is caused by outward loads on the knee joint. For example, if the lower leg is forcibly pushed outwards while the leg is extended due to accidents during football or skiing, this can lead to a tear of the medial collateral ligament. If there is also over-rotation of the knee joint, the cruciate ligaments or the menisci can also be injured, which is known as an "unhappy triad".

Tears of the external collateral ligament (outer ligament) are largely caused by excessive internal rotation of the knee joint. The outer collateral ligament tear occurs much less frequently than the inner ligament tear, but can also be accompanied by damage to the cruciate ligaments or the menisci.

A typical symptom of an injury to the collateral ligaments is the acute pain that subsides after some time. When the knee joint is strained again, however, the pain usually becomes noticeable again. If, in addition to the collateral ligaments, small vessels are also injured, the knee may swell and haematoma formation (bruising) may occur.

Furthermore, patients usually report that their knee feels unstable in the direction of the uninjured collateral ligament. In addition, the leg can be stretched excessively in the direction of the healthy collateral ligament.

A rupture of the lateral ligament can usually be diagnosed by the course of the accident and by special examination measures. Thus, the stability test is usually performed, which can detect excessive deviation of the knee to the healthy lateral ligament. Thus, if the medial collateral ligament is torn, hyperextension to the outside is possible, and if the lateral collateral ligament is torn, hyperextension to the inside is possible.

In order to rule out additional injuries to the cruciate ligaments or the menisci, the knee is examined using further stability tests. In some cases, however, these tests can only be carried out after a few days, when the pain has subsided or the swelling has gone down.

To find out if the collateral ligament itself is torn or if it is torn off the bone, an X-ray is usually performed while the knee joint is stabilized.

For more detailed imaging, for example to check other structures, magnetic resonance imaging (MRI) is best. In rare cases, the diagnosis can also be made by means of an endoscopy of the knee joint (arthroscopy).

If only one lateral ligament is torn, this does not normally need to be surgically repaired. In most cases, stabilisation of the knee joint by means of special splints and strengthening of the leg muscles through physiotherapy are sufficient.

However, if the injury separates the collateral ligament from the bone, surgery is usually necessary, using special wires, nails or screws to secure the ligament. Unhappy triad injuries with involvement of the cruciate ligament or menisci also require surgical repair in most cases.

The outlook after an injury to a collateral ligament is usually good and the tear usually heals very well.

For a complete recovery of the injured collateral ligament, however, consistently performed, regular physiotherapy to strengthen the muscles is important. This can stabilize and relieve the knee joint, whereupon the performance of sports activities often becomes possible again without any problems.