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

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. The knee may feel unstable or weak. Sometimes, the knee may even give way under the weight of the person.

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).

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.

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).

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.

Surgical treatment is often necessary for active people or athletes wishing to return to activity. 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). Surgery is often performed on an ambulatory basis, meaning that the patient can go home the same day.

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..

Full recovery from ACL surgery can take several months. It is crucial not to resume physical activity until the ligament has completely healed, to avoid any risk of recurrence.

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).

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. Don't wait to consult a doctor if you experience these symptoms, as prompt treatment can limit further damage and improve prognosis.

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. 

What is the anterior cruciate ligament (ACL) and what does it do?
The anterior cruciate ligament (ACL) is a ligament inside the knee that connects the femur to the tibia. It plays a crucial role in knee stability, particularly during rotational movements.

Which sports carry the greatest risk of ACL tear?
Sports most at risk include downhill skiing, soccer, basketball and tennis. These activities often involve abrupt changes of direction that can stress the ACL.

What are the symptoms of an ACL tear?
Symptoms include a cracking sound in the knee, intense pain, rapid swelling, a feeling of instability and sometimes a hematoma.

How is an ACL tear treated?
Treatment may include rest, physiotherapy, and in some cases, surgery to reconstruct the ligament.

How to tell the difference between a mild knee sprain and an ACL tear?
A mild knee sprain may cause moderate pain and slight swelling, but an ACL rupture is usually accompanied by an audible crack, intense pain and rapid swelling.

Can ACL tears be prevented?
Although not all ruptures can be prevented, certain preventive measures, such as muscle strengthening, adequate warm-up and the use of protective equipment, can reduce the risk of injury.

What complications can arise after an untreated ACL tear?
Untreated ACL tear can lead to chronic knee instability, cartilage or meniscus tearing, and early osteoarthritis, compromising long-term mobility.