There are 4 ligaments, tough bands of tissues, in the knee that stablise the joint. The most commonly injured ligament is the anterior cruciate ligament (ACL).
Preventing abnormal sideways motion of the knee are the collateral ligaments, the medial collateral ligament (MCL) and the lateral collateral ligament (LCL), which are located on the inside and outside respectively of the knee.
The ACL is the most commonly injured ligament of the knee. It is usually injured in rapid or abnormal twisting motion such as when the knee stops or changes directions suddenly. The ACL can also be injured when the knee twists on landing or as a result of a direct contact or collision such as during a soccer tackle.
Injury to the PCL occurs when direct force is applied to the front of the knee when the knee is bent, such as when the bent knee hits the dashboard in a car accident. The ligament may also be pulled or stretched in a twisting or hyper-extension injury.
Injuries to the collateral ligaments, like the medial collateral ligament (MCL) and lateral collateral ligament (LCL), are usually caused by a direct blow to the side of the knee or a twisting injury. It may occur in isolation or together with ACL or PCL injuries.
Diagnosis is usually made on history and clinical examination. Symptoms include pain and swelling at the site of injury and the knee may feel unstable.
Diagnosis is usually made on history and clinical examination. An x-ray of the knee will rule out associated fractures. An MRI may also be ordered to rule out other injuries to the meniscus or cartilage.