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Tear of the Anterior Cruciate Ligament (ACL) in the Knee

The anterior cruciate ligament*A ligament is a small band of connective tissue that connects two bones to each other in the same joint. creates stability in the knee, in particular during rotational movements. As a result, if it is torn the functional capacity of the joint is immediately limited. Most commonly only one ligament is torn, but it can also affect both. The tear can either be total or partial.


A cracking noise in the knee followed by intense pain and, quite quickly, swelling of the joint are the characteristic signs of an anterior cruciate ligament (ACL) tear.

It is always caused by an injury (for example falling while skiing). The person is often unable to bear any weight on the affected leg and therefore struggles to walk normally. It is also sometimes impossible to bend or fully straighten the knee.

If the injury is complicated, there is a risk of bleeding underneath the skin and bruising (hematoma).

Causes of a Tear of the Anterior Cruciate Ligament in the Knee

An ACL tear is most commonly caused by an accident while playing a sport such as skiing, football, or basketball. The injury occurs during a twist and generally coincides with a sudden change of direction or landing badly from a jump.

Risk Factors

Sports that involve frequently changing direction pose a higher risk of ACL tears. Typically these are ball sports (basketball, handball, and tennis), judo, and above all Alpine skiing. Skiing places a lot of strain on the knee because the foot and ankle are immobilized in rigid boots.

Poor technique when playing sport is another risk factor. It can also be caused by tiredness, insufficient training, and/or poor physical condition. When hiking on uneven ground, for example, a loss of balance and/or coordination can lead to subconscious compensatory movements that expose the knee to a risk of ligament injury.

Finally, women are much more likely to suffer ACL injuries due to their muscle and hormonal differences (increased risk just before ovulation).

Treating a Tear of the Anterior Cruciate Ligament in the Knee

The following measures should be taken as soon after the accident as possible:

  • immobilize the knee with a brace, knee support, or at least an adhesive bandage,
  • apply ice to the joint,
  • take painkillers,
  • if there is significant painful swelling, joint aspiration*A medical procedure in which a needle is inserted into the joint either to remove liquid or inject medication. should be performed..

There are then two possible treatment options: surgery or conservative treatment. Conservative treatment involves resting the joint, physiotherapy, and taking painkillers. It is important to know that this kind of treatment is only effective in 50% of cases, which is why it is reserved for patients who do not move much and who do not wish to get back to physical activity quickly. In comparison, patients who undergo surgery regain better stability in the knee.

Surgery can normally be performed in the weeks following the tear, as soon as the person can walk again without limping. In the case of serious injuries, sometimes surgery is performed as an emergency. In any case, rehabilitation should take place as soon as possible.

The operation consists of reconstructing the ligament using another tendon* Part of the muscle in the shape of a cord that connects the muscle to the bone. (autotransplant or a tendon taken from a deceased donor).

Progression and Possible Complications

If the anterior cruciate ligament (ACL) is not torn but simply sprained, it usually heals within two weeks. In the case of a partial or full tear requiring surgery however, the patient will need to stay in hospital for one or two days and undergo four months of rehabilitation with physiotherapy sessions. How long it will be until previous professional or sporting physical activity can be resumed varies on a case-by-case basis.

The extent of the tear and any associated damage to the inside of the joint will of course affect the prognosis. The injury may lead to chronic instability, a tear of the cartilage*Connective tissue located at the junction between several bones that absorbs the shock from movements. located between the femur and the tibia (meniscus), and early wear of the joint potentially leading to osteoarthritis*Deterioration of the cartilage in the joint..

Preventing Tears of the Anterior Cruciate Ligament (ACL) in the Knee

Making sure your muscles are properly prepared before starting a sporting activity is essential. There are specific strengthening exercises you can do for each muscle group. It is also a good idea to get proper advice when purchasing equipment. When playing a sport that requires technical skill, it is important to learn the right technique. It is however advisable to opt for low-impact forms of exercise (for example cycling and aquafit).

When Should You Contact the Doctor?

If, during an impact or fall, you hear a cracking in your knee, feel pain almost immediately to the extent that you can no longer bear any weight on your affected leg, and you feel like your knee is giving way, it is highly likely that you have ligament damage.

Care at Hôpital de La Tour

A clinical examination of the knee is normally enough to detect an ACL tear. A standard X-ray*A medical imaging technique that uses X-rays to obtain images of different parts of the body. can confirm the diagnosis and specify the exact nature of the damage. This diagnosis will be made by a sports physician or a knee surgeon. In some cases, and particularly if there is suspected involvement of the meniscus or knee bones, an MRI* A medical imaging technique used to obtain 2D or 3D images of the inside of the body. or computed tomography*A medical imaging technique used to obtain a 3D reconstruction of different organs of the body..

MRI is a technique that uses magnetic and radio waves to create 3D images of tissues. Computed tomography also involves performing a scan to obtain cross-sectional images of an anatomical structure using X-ray beams and a computer system. 

The number

Each year, close to 4,400 people suffer from a tear of the anterior cruciate ligament in the knee in Switzerland.

Did you know ?

The knee joint is stabilized by several ligaments that take their name from their position: the lateral collateral ligament, the medial collateral ligament, and two cruciate ligaments, one anterior and the other posterior.


Read our article in Le Temps to find out more.

Who should I see about these symptoms?

We recommend that you see the following health professional(s) :