What is a knee ligament injury?
The ligaments around the knee are strong. However, sometimes they can become injured. They may be stretched (sprained), or sometimes torn (ruptured). A ligament rupture can be partial (just some of the fibres that make up the ligament are torn) or complete (the ligament is torn through completely). The majority of knee ligament injuries are sprains and not tears and they tend to settle down quickly.
There are a number of different things that can cause injury to the ligaments in your knee:
You may have a direct blow to your knee or knock into something with your knee.
Your knee may be moved outside of its usual range of movement. For example, this can happen during a fall, if you land awkwardly during sport, or after a sudden movement.
Medial collateral ligament injury
Injuries to the MCL can happen in almost any sport and can affect people of all age groups. They often happen when your leg is stretched out in front of you and the outer side of your knee is knocked at the same time - for example, during a rugby or football tackle.
Lateral collateral ligament injury
Injuries to the LCL are less common than injuries to the MCL. This is because your other leg usually protects against injury to the inner side of your knee. (It is usually a direct blow to the inner side of your knee that causes an LCL injury.) But, this ligament injury can sometimes happen if one leg is stretched out in front of you and doesn't have the other leg for protection - for example, during a rugby or football tackle.
Anterior cruciate ligament injury
ACL injuries most often occur during sports such as football, basketball, skiing and tennis. The injury often happens if you land on your leg and then quickly pivot or twist your knee in the opposite direction.
Women are more likely than men to injure their ACL although it is not certain why this is. About half of people with an ACL injury also have injury to their meniscus or another ligament in the same knee.
Posterior cruciate ligament injury
Injuries to this ligament are not as common as ACL injuries. This is because the PCL is wider and stronger than the ACL. There are a number of ways that the PCL can become injured. For example, it may be injured during a car accident if the front of your bent knee hits the dashboard. It may also be injured from falling on to your bent knee. Your PCL can also be injured if your knee is hit from the front whilst your leg is stretched out in front of you with your foot on the ground - for example, during a game of football.
At first, some people with a PCL injury may not have much in the way of symptoms (see below). It may take a while for you to realise that there is a problem. For example, you may later notice pain that comes on when going up and down stairs or when starting a run; or, your knee may feel unstable when walking on uneven ground.