What are the anterior cruciate ligaments?

The knee can be thought of as having four ligaments holding it in place, one at each side to stop the bones sliding sideways and two crossing over in the middle to stop the bones sliding forwards and backwards. It is the two that cross over front to back in the middle of the knee that are called the anterior and posterior cruciate ligaments (see image). The anterior meaning front) cruciate ligament prevents the shin bone or tibia popping out the front of the knee and the posterior (meaning back) prevents the tibia from sliding out the back of the knee.

How is the anterior cruciate ligament injured?

The ACL or anterior cruciate ligament is injured either through twisting the knee or through an impact to the side of the knee - often the outside. 
Most anterior cruciate injuries come from a twisting of the knee when the foot is firmly planted on the ground. If the anterior cruciate ligament is injured through impact then it is very likely the medial ligaments, cartilage and other structures will also be injured - known as O'Donohue's triad.

What are the symptoms of an injured anterior cruciate ligament?

* Pain at the time of injury which dies away afterwards.
* Swelling.
* If the swelling comes on rapidly then it could be caused by bleeding within the joint.
* In the later stages when the swelling has decreased there may be instability in the joint.
* For a partial rupture pain may be felt on the Anterior Drawer test where the tibia is pulled

What can the athlete do?

* Apply RICE (Rest, Ice, Compression, Elevation) immediately.
* Seek medical help immediately.
* They will be required to rest for some time and use crutches if necessary.

What can a professional and when is surgery recommended?

* A doctor or sports injury professional can assess the knee and confirm the diagnosis and organise any scans that may be necessary.
* Refer the athlete for surgery or advise on conservative non surgical rehabilitation. Surgery is generally suitable for a young, motivated sports person who is likely to stick to a challenging rehabilitation program. Surgery will involve reconstructing the ligament from a tendon elsewhere in the body, or simply repairing the damaged ligament.
* In older, less active people surgery may not be advised, largely due to the demands they will place on the knee in the future and the likelyhood of sticking to a challenging rehabilitation programme.
* Rehabilitation should start from the time of injury, not necessarily from the time of surgery. This will aid a faster recovery following surgery. If the athlete can get the knee as strong as possible before surgery then this will accelerate rehabilitation following surgery.


An old ligament injury can often cause problems by reoccurring. After resting the injury might have settled down only for it to return when you go back to sport. This can also be operated on if necessary.

What does surgery involve?

* Surgery involves either repairing the anterior cruciate ligament or reconstructing the anterior cruciate ligament. With a repair, the exisiting damaged ligament is sutured (stitched) if the tear is in the middle or if the ligament has come away from the bone (avulsion tear) then the bony fragment is reattached.
* Surgical reconstruction of the anterior cruciate ligament is performed using either an extraarticular technique (taking a structure that lies outside the joint capsule such as a piece of the iliotibibial band) or an intraarticular technique (moving a structure within the knee such as part of the patella tendon which will replace the anterior crucitate ligament).
* Surgical technique is very important to a positive outcome. Placing the acl just millimetres from the correct position can prevent normal motion returning.

Who is usually considered suitable for ACL surgey?

* The competitive athlete or sports person is usually considered suitable because the of ability to stick to a strict rehabilitation programme and the demands they will be placing on the knee following rehabilitation.
* Active people with instability of the knee and unwillingness to alter their lifestyle to compensate for example where hobbies or work require strong knee joints.
* People whose knee is unstable in normal day to day functional situations. For example if it gives way or collapses climbing stairs.
* Individuals who have repeated swelling of the knee as a result.
* People who have tried intensive conservative rehabilitation for 6 months but it has not worked.

How long will the athlete be out of action?

This largely depends on your surgeon or physiotherapists approach to rehabilitation. Some therapists advocate an accelerated rehabilitation programme returning the athlete to full competition within 5 months, others prefer a 9 month rehabilitation period.

Which types of knee brace are available?

A knee support or knee brace provides protection and support. They prevent injury to healthy joints and support unstable joints.

Hinged Knee Braces

A hinged knee brace is likely to provide the best support for the knee and contains metal reinforcements in the sides which are connected by a hinge in the middle. Some knee braces use a geared hinge system in the middle which means the pivot point of the support moves as the knee bends (because the pivot point of the knee changes as it bends) providing a more snug fit.
This provides excellent lateral support to protect the medial and lateral ligaments and knee joint in general. No support can guarantee protection to the anterior cruciate ligament as it only requires just a few degrees of twisting to damage it.

Stabilized Knee Supports

A stabilized knee support has reinforced side panels to provide extra support over the standard knee support - again helping to provent sideways stress on the knee ligaments. Stabilized knee supports may have flexible steel springs sewn into the material at the side or may have elastic straps which wrap around the side for additional support.
A stabilized knee support will provide less lateral support for the knee joint but will often be less bulky than a full hinged knee support.

Basic Knee Supports

A simple neoprene heat retainer will not usually have any additional springs, stays or supports. Some are open patella and have a hole for the patella to fit through. This can decreases the pressure on the kneecap or patella. A padded knee support will be closed and have additional padding over the patella to protect from knocks or minor impact as well as pressure from the ground when kneeling for long periods or landing on the knees for example in volleyball.
These will provide only very moderate support and are not usually sufficient to provide protection to joints where ligament injury has occured or is a risk.

© 2005-2008. Barrie Spirit Soccer
Anterior  Cruciate  Ligament  Injury  -  ACL
We would like to thank Mike and www.sportsinjuryclinic.net for allowing us to publish this article on the Barrie Spirit Soccer website.
Please remember the information on this site is for information purposes only and cannot replace the sports injury specialists.