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Anterior Cruciate Ligament Injury
Anterior 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.
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An ACL sprain is usually caused by a sudden twisting of the knee or from a collision or impact. Symptoms will include:
- Sudden pain in the knee joint at the time of injury.
- There may be an audible pop or crack at the time of injury and a feeling of instability.
- 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. Symptoms will then also include:
- Restricted range of movement with particular difficulty straightening the leg.
- Tenderness all around the knee joint.
- There will be positive signs in the anterior drawer test and Lachman's test.
An MRI scan can confirm the diagnosis and an X-ray can eliminate an avulsion fracture where the ligament pulls a piece of bone away.
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 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.
- 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.
Treatment can be split into immediate first aid at the time of injury and longer term rehabilitation which will often involve surgery.
See acl rehabilitation program for a more detailed step by step approach.
If an ACL injury or knee joint sprain of any kind is suspected then stop play or competition immediately, assuming you have a choice!
- Apply the PRICE principles of protection, rest, ice, compression and elevation. Applying ice and compression will help limit pain and stop bleeding and swelling. Ice can be applied for 10 to 15 minutes every hour for the first 24 to 48 hours although not directly against the skin. Elevating the limb will also help swelling and tissue fluids drain away from the site of injury.
- Some professional therapists at pitch side will immediately apply a compression wrap fairly tightly to prevent the knee swelling up however this should only be left on for 10 minutes at a time to avoid stopping blood flow completely and causing further injury.
- Seek medical attention as soon as possible.
- Electrotherapy treatment such as ultrasound, inferential and tens can begin which may help reduce pain and swelling.
There are a number of commercially available cold wraps which are excellent for knee joint injuries as they provide compression as well as cold at the same time.
The decision whether or when to operate to reconstruct a torn anterior cruciate ligament is a controversial one. Surgery can be performed shortly after injury, a few weeks or even months after injury or not at all.
The decision of whether to operate is based on a number of factors, including:
- the athletes age; lifestyle; sporting involvement; occupation; degree of knee instability and any other associated injuries.
- older people who are less active and perhaps injured their ACL following a fall as opposed to during sport may be unlikely to undergo surgery.
- A younger, fit person who regularly plays sport or needs to be active for work and would be more likely to adhere to a complex rehabilitation program is more likely to be offered surgery.
- Other factors include whether a meniscus repair is required or any other joint injury and the degree of instability in the knee.
See expert interview on ACL surgery for more detailed information.
Mobility 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. Isometric or static strengthening exercises which do not involve movement can usually begin early on.
See more on ACL exercises.
If the knee joint is lacking stability following injury then it can be taped to protect it from further injury prior to surgery and after surgery to give support when returning to normal training.Taping usually provides a higher level of protection than wearing a knee support but for a shorter period of time. The tape will stretch slightly over time and lose its effectiveness.
See acl taping technique.
Supports & braces
A hinged knee brace is often recommended for support both before and after surgery. Often a high level of support with solid metal stays at the sides is recommended. This will give support but cannot completely protect the acl against further injury. There are conflicting opinions on their effectiveness although they are believed to give the patient confidence. Some more expensive braces protect the ligament by preventing rotation of the joint where basic supports cannot. However, even a simple neoprene support can give the patient proprioceptive feedback improving coordination which may help avoid further injury.
See expert interview on acl knee braces.
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