ACL Sprain

ACL Sprain

Anterior Cruciate Ligament injury or 'ACL injuries' are common in contact sports and especially those that are combined with a 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 symptom on the field of play is usually 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.

A professional therapist will do a number of knee assessment tests to help diagnose the injury including the anterior drawer test and Lachman's test.

Read more on symptoms & diagnosis >>>

What is an ACL sprain?

An ACL sprain is a tear to the anterior cruciate ligament in the knee which 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.

It 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 causing excessive movement of the tibia and a torn 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 sprain) or the meniscus (cartilage - medial meniscus tear) and these need to be accurately diagnosed and treated.


If 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 orthopedic consultant to decide whether surgery is indicated.

Immediate first aid for ACL tears involves applying the P.R.I.C.E. therapy principles (protection, rest, ice, compression, and elevation. A cold therapy and compression wrap should be applied for at least the first 72 hours or until a specialist opinion is sought.

A doctor or professional practitioner can make a full diagnosis which may not be possible until swelling has reduced. They are likely to refer you on for MRI scans or X-ray to confirm the diagnosis and refer to a surgeon.

The 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 athlete's age, their occupation, their lifestyle and the degree of instability within the knee, and an orthopedic 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.

Read more on rehabilitation of ACL injuries >>>


Once 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 surgery is performed, as this has been shown to improve the overall outcome.

If surgery is indicated, then pre-surgery exercises 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.

One of the most important aspects of ACL injury rehabilitation is proprioception. 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.

Read more on ACL injury exercises.

ACL reconstruction surgery

Orthopaedic Surgeon Richard Villar talks about surgery for anterior cruciate ligament injury.


Firstly the diagnosis should be confirmed with manual tests and MRI scans. Previously extra-articular operations were undertaken which means tightening a tendon from outside the knee joint to stabilize the joint, rather than repairing the ACL itself. The majority of operations are now Intra-articular reconstructions where a graft is used from either the patella tendon or the semitendinosus (hamstring) tendon. These are known as bone-tendon-bone grafts as the graft of tendon is attached to bone 'plugs' at each end. Artificial ligaments and donated ligaments are also occasionally used.

Who should have surgery?

It was previously believed that the ACL did not play a hugely important role in stabilising the knee joint and so ruptured ligaments may have been removed. This now does not occur as the importance of the ACL in knee joint stability is now fully understood. However, surgery is not undertaken in every case. The decision to forego surgery is based on the stability at the knee, the patient's age and the activities or occupations they are involved in. Many people choose to try to stabilise the knee by building up muscle strength, especially in the Quadriceps. In addition, knee braces which work to prevent rotation can also be used. These are particularly popular in high impact activities such as skiing.


ACL Surgery recovery and ACL reconstruction recovery are extremely variable, but generally, it can be expected that within 4-5 months the knee is starting to function normally and kicking movements and sudden turns may be possible. Even 1-year post surgery the knee may feel almost normal but total perfection is rare, it may still result in minor niggles every now and again.

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 by the professional athlete.

View expert interviews.

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Exercises for ACL Rehabilitation

Mobility and strengthening exercises which are used as part of an ACL rehabilitation program are outlined below. Exercises can be done as soon as pain allows both before surgery and after.

ACL Sprain Rehabilitation

If an ACL injury is suspected, we strongly advise you seek a professional medical opinion as soon as possible to confirm the diagnosis and refer to an orthopedic consultant to decide whether surgery is...

Taping for ACL Injuries

Physiotherapist Neal Reynolds demonstrates a general knee taping technique which can be used to help support and ACL ligament injury.

ACL Injury Assessment & Diagnosis

An ACL injury is usually caused by a sudden twisting of the knee whilst the foot is planted on the ground, or a direct impact or trauma to the knee, often on the outside of the joint.