Anterior Cruciate Ligament (ACL) Injuries
The ACL is a cross shaped ligament within the knee joint which attaches the tibia to the femur.
Its primary function is to prevent anterior tibial translation (forward movement of the tibia away from the knee joint). It also acts as a restraint to tibial rotation and varus/valgus distortions
When the ACL is injured, a combination of anterior translation and rotation occurs.
ACL injuries are common to most sports, and more common in females than males.
They may be either contact or non-contact.
In contact injuries, there is usually a valgus force creating an abnormal pressure on the knee joint which tends to result in damage to the ACL, Medial Collateral Ligament (MCL) and the meniscus; although meniscal involvement is thought to occur later due to chronic deficiencies in the ACL.
Damage to the collateral ligaments may also be involved.
In the non contact injury a popping sound can often be heard often happening where there is a sudden change in direction or landing from a jump.
Very often a large haematoma will develop within a few hours.
High risk sports such as football, rugby, basketball and skiing increase the chance of ACL injuries, while females are more susceptible to this injury than males. Research into this gender difference is ongoing, and while current reasoning is inconclusive, the increased occurrence among women can be quite dramatic.
Variations in the shape of the femoral intercondylar notch have been shown to be important in the occurrence of non contact ACL injuries, and research has determined that the femoral notch and Anterior Cruciate Ligament in women is significantly smaller than in males.
Footwear, in particular the use of particular formations of studs on artificial turf may result in an increased risk of ACL injury.
Determination of an ACL injury must be performed by an experienced professional, and should include the following:
Initial assessment should look for abnormality of the bone and severe swelling. Immediate effusion, indicates intra-articular trauma, and in the absence of bone trauma shows a good correlation with ACL injury
Range of motion looking for incomplete extension
Palpation to determine collateral ligament, MCL and meniscus involvement.
Lachman, Pivot Shift, and Anterior Drawer tests to investigate laxity in the ligaments
Physiotherapy tends to be directed towards strengthening the quadriceps and hamstrings while range of motion exercises are indicated to help reduce effusion and improve strength and mobility.
Surgery nowadays includes a variety of different grafting techniques to restore function.
Patients who are not suitable for reconstruction may have arthroscopy to debride the remaining ligament to facilitate increased motion.
Post injury, patients may use an ACL Knee brace as part of their rehabilitation programe which often gives them added confidence when getting back to sport.
ACL injuries are relatively common in skiing where knee support is important due to the forces applied to the ligaments in this common sports injury. Using a good skiing knee brace will also offer support for the collateral knee ligaments which are particularly vulnerable in skiing