Knee Ligament Injuries

There are four major ligaments in a knee along with several supplementary ligaments. They are all important in stabilising the knee.

The main ones are the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral (MCL) and the lateral collateral (LCL).

Lateral collateral ligament injuries

The LCL is often injured at the same time as other ligaments such as the anterior or posterior cruciate ligaments, and is often damaged when a player is standing on the knee when tackled from the medial side. If it is not treated properly then the knee will have chronic lateral instability and may develop early arthritis.

Medial collateral ligament injuries

The medial collateral ligament (MCL) is the most commonly injured ligament in the knee. It runs down the inside of the joint as a strap to stop the knee buckling in an inwards direction.

The MCL may be damaged when the knee is hit from the lateral side such as in a rugby tackle.

Most MCL injuries can be treated without knee surgery but may require a brace or physiotherapy. For the best results early treatment is necessary.

Knee Ligament Diagram
Torn Anterior Cruciate

Anterior Cruciate Ligament Injuries

The anterior cruciate ligament (ACL) is an important ligament that lies within the knee joint and stops the shin bone moving forwards from under the thigh bone. If it gets damaged then the knee may become unstable and give way or collapse especially in movements that involve turning on a flexed knee.

The ACL usually tears when a sportsperson suddenly changes direction when running such as when playing rugby, football or netball and most commonly there is no external contact at the time. As it tears the patient often hears a popping sound, the knee collapses and then swells up within a few hours. With rest the swelling will settle and the knee becomes more comfortable, but then when sport is resumed the same thing happens again when it gives way.

Patients who have damaged their ACLs need assessment and those that have repeated episodes of instability or who wish to return to active sports may benefit from a reconstruction of the ligament. However 20% – 30% of patients with torn ACLs can return to their day to day activities without major problems.

Unfortunately when the ACL goes there is often other damage to the knee at the same time such as a torn meniscus or joint surface damage which also may require treatment.

Posterior Cruciate Ligament

Posterior Cruciate Injuries

The posterior cruciate ligament (PCL) is not injured nearly as frequently as the ACL. As the name implies it lies at the back of the knee and stops the shin bone slipping backwards under the thigh bone on weight bearing.

It is usually damaged when the knee is over straightened (hyper-extended) such as when there is a blow to the front of the knee when standing on it. Dashboard injuries also can tear the PCL.

Generally PCL injuries can be treated with physio provided no other structures have been damaged at the same time.