Cruciate ligament rupture

Accidents in ball sports or skiing are usually the reason for a cruciate ligament rupture. Women are more often affected by them than men. Whether surgery is required on a cruciate ligament rupture depends on the extent of the injury, the stability of the knee and the age of the injured person, among other factors.

At a glance

  • The anterior cruciate ligament is one of four large ligaments that keep the knee stable – and the most commonly ruptured.
  • Ruptures are usually caused by sports injuries, for instance as a result of a fall when skiing or a twisted knee when playing soccer.
  • Cruciate ligament ruptures are more common in women than men.
  • Whether surgery is required depends on the extent of the injury, the stability of the knee, and the age of the injured person, among other factors.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

An injured footballer lies on a sports hall floor.

What is a cruciate ligament rupture?

The anterior cruciate ligament is one of four large ligaments that keep the knee stable – and the most commonly ruptured. Most cruciate ligament ruptures are caused by sports injuries, for instance as a result of a fall when skiing or a twisted knee when playing soccer.

A rupture of the anterior cruciate ligament does not always require surgery. Whether an operation is required depends on the extent of the injury, stability of the knee, and the age of the particular person affected, among other things. The injured person’s personal situation also plays an important role in the treatment. For example, the occupation or sports that should still be carried out have an influence.

Ruptures of the posterior cruciate ligament are far rarer. These are not covered by this article.

What are the symptoms of a cruciate ligament rupture?

When the anterior cruciate ligament ruptures, a snapping or popping sound can often be heard. The knee normally swells up immediately thereafter. It is painful, especially during movement.

Many of those affected can walk normally after a cruciate ligament rupture, but the knee feels unstable, as though the upper and lower leg were shifting slightly. This feeling occurs for example when the knees are being bent and during sideways and rotary movements. But also when the affected leg has the body’s full weight put on it during stair climbing.

In around 90% of all cruciate ligament ruptures, in addition to the anterior cruciate ligament, other knee ligaments or cartilage are also injured:

  • In 50 to 75% of cases, one or both menisci
  • In about 50% of cases, the articular (joint) cartilage
  • In about 15% of cases, the medial collateral or lateral ligament of the knee

Furthermore, the bones are usually bruised. This injury most commonly involves severe pain and other discomfort.

What are the causes of a cruciate ligament rupture?

The anterior and posterior cruciate ligament, along with the lateral and medial collateral ligament, connect the upper and lower leg bones.

The anterior cruciate ligament has the following tasks:

  • It stabilizes the knee and prevents the tibia from shifting forward.
  • Along with the posterior cruciate ligament, it prevents the knee from twisting. For that reason, the cruciate ligaments wrap themselves around each other and stabilize the knee.

The anterior cruciate ligament moreover has special sensory cells (receptors) that control muscle reflexes in order to stabilize the knee.

If severely strained, the anterior cruciate ligament can rupture, for example if:

  • the knee twists with force – such as when slowing down quickly from a run, a rapid change in the direction of movement or if the leg with weight on it gives way inwardly.
  • an unfortunate landing with stretched leg after a jump.

What are the risk factors for a cruciate ligament rupture?

Cruciate ligament ruptures occur in particular with sports like soccer, handball, volleyball, basketball, and skiing.

Women playing ball sports have a higher risk for cruciate ligament ruptures than men. One of the things that doctors debate is whether this could be due to women often having weaker hamstrings.

How often does a cruciate ligament rupture occur?

Most cruciate ligament ruptures occur in ball sports. Sportspeople aged 15 to 45 years are especially affected. 

Most cruciate ligament ruptures occur in ball sports.

A summary analysis of more than 50 studies involving people who play ball sports has revealed that 3 to 4% of women and 2% of men injure their cruciate ligament at some point. 

How does a cruciate ligament rupture progress?

If a cruciate ligament rupture is successfully treated, the knee functions again normally or almost normally in about 80 to 90% of those affected. Once the injuries have healed, most people engage in sports again. However, the fear of another injury leads to about 20 to 30% of people subsequently deciding to play a different sport or to engage in less intensive sports – even though this is often unnecessary. 

What are the potential consequences of a cruciate ligament rupture?

A cruciate ligament rupture increases the long-term risk of prematurely developing arthritis of the knee – especially if the menisci were also injured. 

A summary of studies conducted over a period of more than 10 years has shown that after a cruciate ligament rupture, an X-ray showed clearly visible osteoarthritis that had developed in the knee in about 20% of study participants. Without a cruciate ligament rupture, this amount is only about 5%. However, the risk for arthritis of the knee does not depend on how the injury is treated.

Furthermore, visible changes on an X-ray do not necessarily mean discomfort: other studies have shown that X-rays often say little about symptoms. Anyone who has a cruciate ligament rupture can moreover ensure a well-functioning knee with exercises.

How can cruciate ligament ruptures be prevented?

Certain exercises prior to playing sports can prevent ruptures of the anterior cruciate ligament. These include special programs with warm-up exercises and exercises for strengthening the core and leg muscles, as well as workout elements to improve balance, coordination, and explosive strength.

For example, professional medical associations recommend the “FIFA 11+” program available from the German Football Association (DFB) and the “Stop-X” program developed by the German Knee Society (Deutsche Kniegesellschaft).

These kinds of programs were developed for sports like soccer or handball, which are associated with an increased risk of a cruciate ligament rupture. They are especially worthwhile for active sportspeople as the injury risk involved in ball sports depends on the intensity of the training and the number of competitions.

How is a cruciate ligament rupture diagnosed?

To diagnose a cruciate ligament rupture, the doctor initially asks about the circumstances of the accident and symptoms. The knee is then palpated and examined further. To check the stability of the knee, the upper and lower leg are moved.

When necessary, magnetic resonance imaging (MRI) provides accurate pictures of the knee with the ligaments and menisci. An X-ray can reveal whether bones are broken – but not whether ligaments are ruptured or damaged.

How is a cruciate ligament rupture treated?

First of all, the knee needs rest after a cruciate ligament rupture. It should therefore be elevated and cooled immediately after the accident until the acute pain and swelling subside.

A pressure bandage can also be useful. The same is true of non-steroidal anti-inflammatory drugs such as ibuprofen. Later on, a walking aid can help relieve stress on the knee – especially if it is very unstable.

There are two options for treating a ruptured cruciate ligament:

  • With conservative treatment under physiotherapeutic guidance, the knee muscles should be strengthened so that they compensate for the function of the ruptured cruciate ligament. Whether this treatment is possible depends on whether other knee structures are injured, and if so, which.
  • With an operation, the ruptured cruciate ligament is replaced. Surgery is carried out in the form of an arthroscopy, during which small surgical instruments are inserted around the knee through several incisions.
Treatment options for a cruciate ligament rupture: rest, elevation, and cooling, walking aids, anti-inflammatory painkillers, physiotherapy, surgery

If surgery is required on the knee, there is normally a wait of 2 to 4 weeks after the accident before this is performed. In this period, the swelling may subside and the knee may settle down.

If the knee is still stiff, swollen, or inflamed during the operation, the tissue in the knee may harden and later restrict movement. The flexibility of the knee muscles must therefore be improved before the operation with suitable exercises.

Following surgery, a 4 to 12-month healing and training phase is required, depending on the sport.

So far only one major study exists that has compared conservative treatments with surgical ones. The result: conservative treatment achieved long-term success for more than 50% of those affected. For an operation however, the success rate is 80 to 90%.

According to current knowledge, there are no disadvantages for the knee function if the knee is initially treated conservatively and only later operated on if necessary. However, there is a somewhat higher risk of further injuries, for instance to the menisci, after conservative treatment.

A physiotherapist treats a man’s knee joint

What is the rehabilitation process after a cruciate ligament rupture?

After an operation, it takes months for a cruciate ligament replacement to fully heal and be up to its tasks again. Strong thigh muscles are important for easing strain on the cruciate ligament replacement and stabilizing the knee.

The aim of rehabilitation (rehab) is to strengthen the muscles and get the knee used to the new cruciate ligament. Some time may pass until feeling returns to the knee and it can be moved as naturally as before the accident.

If there is no operation on the cruciate ligament, rehab helps build up the muscles with targeted training to the extent that the knee remains stable. Physiotherapy is therefore useful for all treatments.

Important: If surgery was performed on the knee, it is usually possible to start playing gentle sports again after 4 to 6 months. More intense ball or combat sports are normally only possible after 9 to 12 months. If the knee is treated conservatively, the period of convalescence is reduced by about 2 to 3 months.

Many people find it difficult to accept that it takes a long time and a lot of effort to regain their former fitness after rupturing their cruciate ligament. As such, in addition to consistent training, patience is an important requirement for successful rehabilitation.

More detailed information about rehabilitation after a cruciate ligament rupture can be found at

What else is important in relation to a cruciate ligament rupture?

It is helpful to implement certain measures in preparation for the rehabilitation period even before surgery on a cruciate ligament rupture. These can include:

  • practicing moving with walking aids (crutches) even before the operation
  • getting rid of potential obstacles or trip hazards in the home early on: for example, it can be sensible to avoid stairs by sleeping in another room during the period of convalescence
  • getting to work, school, or university in a different way: depending on the affected leg and the severity of the injury, people may not be able to drive again for weeks
  • organizing help with everyday routines, for instance shopping or other chores
  • sourcing a small shower stool in order to shower sitting down

People who have to use walking aids a lot can sometimes develop other issues, such as muscle soreness or tension in the back, neck, or shoulders. Such issues can also be prevented by working out before the operation.

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen – IQWiG).

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