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ACL Tear

Anterior cruciate ligament ACLAnterior Cruciate Ligament injury or 'ACL injuries' are common in contact sports and especially those that are combined with sudden change of direction such as soccer or football.

Often ACL tears do not occur in isolation and are in most cases are associated with damage to other structures within the knee such as the cartilage or the collateral ligaments.

Torn acl symptoms

ACL tears usually occur as a result of a twisting action where the foot is planted in the ground and the knee turns excessively inwards. The main acl tear symptoms on the field of play usually consist of a sudden pain in the knee and in most cases the athlete is aware that something serious has happened. Patients often complain of an audible pop or crack at the time of injury.

Following the injury, the athlete may have a feeling of instability in the knee and swelling will usually develop rapidly (but not in all cases). The swelling is caused by an excess of blood in the joint and is due to rupturing of the blood vessels around the ACL which causes bleeding within the joint which will also make the joint warm to touch.

ACL assessment video - anterior drawer testAthletes’ that have sustained a torn acl will usually present at a hospital or doctor’s clinic within a couple of days of the injury by which time the joint may be very swollen and stiff. This can make the assessment of the knee more challenging however a skilled clinician can still often make an accurate diagnosis and in some cases, an MRI scan is required to confirm diagnosis.

Specific tests such as Lachman's test and the anterior drawer test can be done to aid diagnosis. In addition to the presence of swelling, there may be associated restriction of movement within the knee and in particular difficulty in straightening the leg. In the majority of cases, the knee is not tender to touch as the ACL is located deep within the knee joint and cannot be felt from the outside.

Do I need surgery?

ACL assessment video - anterior drawer testThe decision on whether or not to operate on ACL tears and if so, when to operate is a controversial one. The overall decision on whether to operate depends on a number of factors such as the athletes age, their occupation, their lifestyle and the degree of instability within the knee, and an orthopaedic surgeon will be able to advise on which treatment approach is preferable.

If reconstructive surgery is chosen, then the operation is either as soon after the injury occurred as possible or alternatively a few weeks down the line when the knee has settled down and the swelling has significantly reduced.

Play video on surgery for ACL surgery injuries and a video by world renowned sports surgeon Mr. Richard Villar...

Home Treatment

Cold therapy wrapIf a torn acl is suspected, we strongly advise you seek a professional medical opinion as soon as possible to confirm the diagnosis and refer to an orthopaedic consultant to decide whether surgery is indicated.

However, you can start to treat the injury at home. Immediate first aid for ACL tears involves applying the P.R.I.C.E. therapy principles. A cold therapy and compression wrap should be applied for at least the first 72 hours or until a specialist opinion is sought. P.R.I.C.E. stands for Protection, Rest, Ice, Compression and Elevation and is used for almost all sports injuries.


Hinged knee braceProtection of the torn or sprained ligament is vital to prevent further damage and to enable the healing process to begin as efficiently and effectively as possible. We advise using crutches to minimise weight bearing through the knee joint and to wear a protective hinged knee brace to limit the movement in the knee and provide additional support to the joint.


Following an ACL injury, REST is one of the most important components of P.R.I.C.E but is so often neglected or ignored. With this kind of injury, an athlete must stop training immediately and allow the injured area to start healing. ACL injuries usually result instability within the knee and therefore by continuing to exercise this may result in further injury and possibly sustaining injuries to other ligament and structures within the knee or surrounding joints. Until the knee has been fully assessed by a doctor or professional therapist, the athlete should minimise the amount of walking they do and ideally use crutches during this period.


Cold knee wrapIce therapy, also known as “cryotherapy”, is one of the most widely known and regularly used treatments for acute sports injuries. It is cheap, easy to use and requires very little time to or expertise to prepare. In the acute stages, the application of an ice pack to the knee can substantially limit the inflammatory reaction that naturally occurs after such an injury and allows the body to start healing the ligament and thereby reduces the overall recovery time.

  • Icing 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 and this is then wrapped in a damp towel before applying. 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 (called “endangerment sites”) and these 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. If in any doubt, seek advice from your therapist or doctor.


Applying compression to the injury will help to minimise the amount of swelling by compressing the blood vessels. Compression can be applied through a number of methods and the most cost-effective is by using a compression bandage which is an elasticated bandage that fits around the affected limb. Using a knee brace can often “double” up by providing both additional support and compression at the same time.


Elevation is the final principle used of P.R.I.C.E. and is equally as important as the other 4. Elevation of the leg above the level of the heart allows gravity to drain the fluid away from the injured knee. In addition to reducing the size of the joint, this may in turn decrease the pain associated with the swelling (also known as “oedema”).

Read more on ACL tear rehabilitation.

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Heel slide exercisesOnce a diagnosis has been made and the initial acute injury management stage has passed, the first stage of ACL injury rehabilitation is to regain normal movement back into the injured knee through mobility exercises. In cases where surgery is the treatment of choice, the surgeon will want the swelling to be reduced and normal knee movement to be regained before reconstructing the ligament, as this has been shown to improve the overall outcome. It is very important that exercises to regain movement in the knee are not too aggressive or they may delay or significantly affect the healing of the damaged ligament and / or irritate the joint, delaying the surgery further.

If surgery is indicated, then pre-surgery strengthening exercises as well as mobility are advised for two reasons - to build up the strength in the muscles around the joint and to regain normal movement, both of which could result in a much better outcome after surgery.

If surgery is not indicated, then mobility and strengthening exercises are advised to slowly return the knee back to normal as safely as possible but not compromising the healing process.

Read more on ACL injury exercises.


One of the most important aspects of ACL injury rehabilitation is proprioception. Exercises to teach the knee “where it is in space” and to facilitate the surrounding muscles to react quickly enough to prevent further injury should be performed progressively throughout the rehabilitation process and can be demonstrated by your therapist.

See more on basic proprioception exercises.

We would always advise seeking a professional medical opinion before starting any exercises post injury.


Knee ligaments explained video

Play knee ligament video

There are four main ligaments that give stability to the knee joint. The two collateral ligaments are located on the inside and outside of the knee and are extra-capsular (outside the knee joint capsule) and prevent excessive sideways movement. The other two are the cruciate ligaments which are intra-capsular (within the knee joint) and cross over in the middle of the knee joint and prevent excessive forward and backward movements.

The anterior cruciate ligament runs diagonally from the back of the femur (thigh bone) upwards and forwards to the front of the tibia (shin bone) and prevents the shin bone from moving excessively forward.

The posterior cruciate ligament passes in the opposite direction and crosses the ACL in the middle of the knee, hence the name cruciate which means “cross-shaped”. Together, these two ligaments are vitally important to the stability of the knee joint, especially for contact sports and those that involve fast changes in direction.

The ACL comprises of two ligaments that are twisted together, called the anteromedial and posterolateral bundles. One of the bundles is tight when the knee is bent and the other is tight when the knee is straight and each bundle limits different movements. For this reason, reconstructive surgery involves replicating this and the graft (replacement ligament) is made up of “two bundles” to form one ligament.

An ACL tear usually occurs as a result of either a twisting force being applied to the knee whilst the foot is firmly planted on the ground or twisting of the knee when landing from a jump. They can also occur from contact situations as seen in sports such as rugby or football, but these are less common. In these situations, a direct blow to the outside of the knee causes the knee to buckle inwards and the same excessive movement of the tibia as seen in the non-contact scenario, and tears the ACL. With this type of injury there is often associated damage to other structures within the knee joint such as the medial collateral ligament (MCL) or the meniscus (cartilage - medial meniscus tear) and these need to be accurately diagnosed and treated.

Expert Interviews

Experienced sports physiotherapist Neal Reynolds talks to about ACL injury prevention, treating ACL tears including choosing the right knee brace and the rehabilitation process and additionally how they are managed in the professional athlete.

View expert interviews.

(page updated 2nd Feb 2016)

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