Hinges are excellent tools that allow one specific type of movement, such opening and closing a door. But they have limited range of motion, and can be damaged when forced to move the wrong way.
This is the case with your knee joint, which is a hinge joint. In order to provide stability and balance for our body, the knee only moves about 180 degrees in one direction. If it’s forced beyond this normal range of motion, this is known as knee hyperextension.
The main parts of the knee that prevent hyperextension are its 4 ligaments, particularly the anterior cruciate ligament (ACL). So it makes sense that when knee hyperextensions occur, the ACL and other ligaments are the most likely tissues to be injured. There can also be damage to the cartilage, muscles, and other soft tissues, but the ligaments bear the brunt of hyperextension injuries.
What causes knee hyperextension?
Knee hyperextension can happen to anyone, but it’s most likely to occur to athletes who play contact sports like football or soccer. That’s because they are often caused by impacts to the front of the knee, such as when a football player is tackled by the legs.
Non-contact sports like skiing can also result in knee hyperextensions if too much force is placed on the knee from the wrong angle.
Treating knee hyperextension
Usually, the symptoms of knee hyperextension are immediate and acute. They include:
- Knee pain, which is sometimes localized near the affected ligament
- Knee instability or weakness
- Limited mobility of the knee
- Knee swelling
- Eventual bruising
Knee hyperextensions initially should be treated in the same manner as nearly all sports injuries: NSAID medications to control pain, and the RICE (rest, ice, compression, elevation) protocol.
In severe cases of knee hyperextension—for example, if the ACL in partially or completely torn—surgery can be used to repair the ligament.