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Anterior Cruciate Ligament Injury

Anterior cruciate ligament ACLAnterior cruciate ligament sprains are common in contact sports and those involving a sudden change of direction. Often an ACL injury will occur in combination with injury to other structures in the knee joint and require immediate first aid.


Symptoms may include sudden pain in the knee joint at the time of injury with an audible pop or crack. The athlete may have a feeling of instability and rapid swelling may occur from bleeding within the joint which will feel warm to touch.

Often an athlete will seek professional advice at a clinic the next day or two after injury. By that time there will be considerable swelling making it very difficult to diagnose exactly what is wrong with the knee. After a few days when the swelling has gone down it will be easier to examine the knee joint.

There will be restricted range of movement with particular difficulty straightening the leg. Tenderness or pain may be felt all around the knee joint and there will be positive signs in the anterior drawer test and Lachman's test.

Anterior draw test

LachmansWith the patient laying on their back with the injured knee bent to 90 degrees and the foot flat on the table. The practitioner may stabilize the foot by sitting on it.The practitioner will grasp the upper Tibia (shin bone) with both hands. They will then attempt to pull the Tibia forwards, towards them. A positive result is if the Tibia moves excessively forwards.The injured knee should always be compared to the healthy knee for 'normal' movement.

Lachman's test

The patient lies on their back with the knee flexed between 15 and 30 degrees. The practitioner grips the outside of the lower femur or thigh bone with the upper hand and the inside of the upper Tibia with the lower hand. The femur is stabilised with the upper hand as the lower hand applies an anterior force on the tibia. A positive result is found if the tibia moves excessively forward compared to the healthy knee.

As well as the tests described above, the practitioner may also test the range of motion at the joint, the strength of the surrounding muscles, and test for associated injuries such as meniscus tears.

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Immediate first aid at the time of the injury consists of the P.R.I.C.E. therapy principle. This should be applied at home for at least the first 2 - 3 days. P.R.I.C.E. stands for Protection, Rest, Ice, Compression and Elevation.

  • Protection - Protect the knee injury from further damage. Where applicable, use of a knee support, perferably a hinged knee support is recommended.
  • Rest - Refrain from exercise and try to reduce the demands of your daily activity to encourage recovery.
  • Ice - The topical application of ice or cold therapy to the area of the knee injury/swelling can assist in reducing the symptoms of pain and inflammation.
  • Compression - The use of a compression support or compression bandages to the knee can can help reduce swelling.
  • Elevation - Keeping the knee elevated above heart level whenever possible to help reduce swelling due to the effects of gravity.


Protection of the damaged tissue is vital to prevent further damage and enable the healing process to start efficiently and effectively. Wear a hinged knee support to limit movement and support the joint.


In the early stages, rest is one of the most important components of the P.R.I.C.E principle but is often neglected or ignored. It does not only refer to the prolonged period of time that the athlete will be out of action but also to the immediate period after the injury. An athlete must know when to stop training and allow the injured area to heal otherwise repetitive minor injuries can often result in a more severe injury that keeps the athlete out for much longer. If an injury is sustained during sporting activity some athletes have a tendency to 'run it off'.


Ice therapy, also known as cryotherapy, is one of the most widely known and used treatment modalities for acute sports injuries. It is cheap, easy to use and requires very little time to or expertise to prepare. The application of ice to an injury, in the acute phase can substantially decrease the extent of the damage. It achieves this in a number of different ways:

  • Decreases the amount of bleeding by closing down the blood vessels (called vasoconstriction).
  • Reduces pain (pain gate theory)
  • Reduces muscle spasm
  • Reduces the risk of cell death (also called necrosis) by decreasing the rate of metabolism

Ice is usually applied to the injured site by means of a bag filled with crushed ice which is wrapped in a damp towel. The damp towel is essential as it forms a barrier between the bag of ice and the skin and reduces the risk of an “ice burn”.  DO NOT leave the ice on for more than 15 minutes as you could cause an “ice burn”.

There are a small number of areas that you should not apply ice to which include the neck, the outside bone of the elbow, the collar bone (upper end), the front of the hip (bony part) and the outer bone of the knee.  The reason for this is there is a superficial nerve just below the skin in these areas that can be damaged by applying ice to it. Always check for contraindications.


Applying compression to an injured area minimises the amount of swelling that forms after an injury and should be applied for the first 24 to 72 hours from the onset of injury. Compression can be applied through a number of methods. The most effective of these is by using a compression bandage which is an elasticated bandage that simply fits around the affected limb.


Elevation of the injured limb is the final principle of PRICE but is equally as important as the other 4. Elevation allows gravity to drain the fluid away from the injured site. This aids in decreasing the swelling which in turn may decrease the pain associated with the oedema (swelling).

Taping the knee can provide support and protection as can wearing a hinged knee brace or support. Often surgery is required which is followed by a longer rehabilitation program consisting of mobility and strengthening exercises.

Read more on treatment and rehabilitation....

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Heel slide exercisesMobility and strengthening exercises are important after the acute stage has passed and normal activities are pain free. If surgery is indicated then pre-surgery exercises are done to build up the strength in the muscles around the joint which could give a much better outcome after surgery.

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There are four main ligaments supporting the knee joint. The lateral ligaments on the inside and outside of the knee which prevent sideways movement and the cruciate ligaments which cross over in the middle of the knee and prevent forwards and backwards movement.

The lateral ligaments on the inside and outside of the knee which prevent sideways movement and the cruciate ligaments which cross over in the middle of the knee and prevent forwards and backwards movement. The ACL runs from the back of the thigh bone to the front of the shin bone and prevents the shin bone from moving forward.

The posterior cruciate ligament passes in the opposite direction forming a cross shape, hence the name cruciate ligaments. Together these two ligaments are vitally important for the stability of the knee joint, especially in contact sports and those that involve fast changes in direction.

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A torn ACL usually occurs through a twisting force being applied to the knee whilst the foot is firmly planted on the ground or upon landing. A direct blow to the knee, usually the outside, as may occur during a football or rugby tackle. If this happens then there is usually also a tear of the medial ligament on the inside of the knee, a medial meniscus tear or articular cartilage injury.


SurgeonsThe decision whether or when to operate to reconstruct a torn anterior cruciate ligament is a controversial one. Surgery may be performed shortly after injury, a few weeks or even months after injury or not at all and may depend on the athletes age, lifestyle and degree of instability.

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Expert interviews

Professional Football Physiotherapist Neal Reynolds talks about prevention, treatment and rehabilitation of anterior cruciate ligament injuries and how the are managed in a professional sports team as well as how to choose a suitable knee brace.

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Stabilized Knee SupportWe recommend a number of products which can help with treatment of anterior cruciate ligament injuries. A cold therapy compression wrap is excellent for applying immediately after injury and can be used throughout the rehabilitation process to help reduce pain and swelling.

A good hinged knee brace can give support and protection, particularly if other structures such as the lateral ligaments are damaged as well, although no brace can guarentee to prevent an ACL injury.