An anterior cruciate ligament (ACL) tear is one of the most common knee injuries. The bones of the knee joint are connected by ligaments which help to hold them together and keep the knee stable.
There are four main ligaments in your knee – those on the outside of the joint (the medial collateral ligament and the lateral collateral ligament) and those inside the joint (the anterior cruciate ligament at the front and the posterior cruciate ligament at the back). The cruciate ligaments control the way the knee bends. The anterior cruciate ligament, which runs diagonally across the knee, allows you to rotate the knee while the posterior cruciate ligament keeps the shinbone in place and prevents it from moving backwards too far.
Causes of ACL tears
The ACL can become torn or sprained, particularly during certain types of high impact sports. Common causes of ACL injury include stopping or slowing down abruptly, sudden changes of direction, landing heavily after jumping, or a collision while running. Female athletes are more at risk than their male counterparts and you may also be susceptible to injury if you have a misaligned pelvis or lower legs, or looseness in the ligaments.
Symptoms of ACL tears
Some people who tear their ACL hear a popping sound and the leg may give way. The knee may feel painful and swollen. Depending on the severity of the injury, the pain might range from mild discomfort when walking through to a loss of strength and movement in your knee. It is very important to get a proper diagnosis as ignoring your symptoms may worsen your knee damage. Also, nearly half of all ACL injuries are accompanied by damage to other parts of the knee, such as the meniscus, articular cartilage or other ligaments, so you will need a full assessment to determine the extent of your injuries. Whatever injuries you have sustained will require proper diagnosis and treatment to prevent more serious damage to the knee joint.
How ACL tears are diagnosed
Following a physical examination and discussion of how and when your symptoms began, the doctor may send you for an X-ray to confirm that there are no other injuries that could be causing you pain, such as a fracture. You may also be given an MRI scan to assess whether there are any other soft tissue injuries.
ACL injuries are graded according to how severe they are. A grade 1 sprain means the ligament has become stretched but is still able to support the knee joint. With a grade 2 sprain, the stretching has resulted in the ligament becoming loose or partially torn. In the case of a grade 3 sprain – the most severe ACL injury – the ligament has been torn in half or wrenched off the bone. With a grade 3 sprain the knee joint will be unstable and very painful. The most common ACL injuries are grade 2 and 3.
Treating ACL injuries
Treatment for an ACL injury will depend on its severity and the age and lifestyle of the patient. In the case of partial ACL tears, the injury usually heals by itself within three months, following a period of rest and rehabilitation. However, patients with this type of injury may continue to experience instability of the knee joint which may require treatment. Your doctor may recommend wearing a hinged knee brace and ongoing physiotherapy, although in some cases surgical repair may still be required.
Reconstruction surgery for ACL tears
If you completely tear your ACL, you are likely to need surgery to prevent ongoing knee instability which may cause further damage to the structures of your knee including the meniscus and articular cartilage. An ACL that is completely torn or wrenched away from the bone may be replaced with a tendon graft, either from elsewhere in the patient’s own body or from a tissue donor.
ACL reconstruction surgery may be recommended for adult patients with active lives or who regularly participate in sports. Children and adolescents may also require surgery although the orthopaedic surgeon will weigh up the advantages of reconstruction against possible problems with bone growth following surgery. If there is a high risk of developing damage to other structures of the knee joint if the ACL injury is left untreated, or if there are already other injuries, your surgeon will recommend ACL reconstruction.
Post-surgical outcomes
After surgery you will need to follow a programme of physiotherapy exercises to build strength and flexibility in the knee joint and to support healing. Depending on how well you recover after surgery, you can normally return to participation in sports within six to 12 months.
For more information about ACL injuries and for advice on diagnosis and treatment, contact us.
