 ACL Frequently Asked Questions1. What is the function of the anterior cruciate ligament (ACL)? The ACL is the most important structure in the knee for providing stability during sporting activities which involve changing of direction while moving at speed (including football, tennis, skiing). If the knee is unstable, cartilage wear & tear occurs at a much faster rate than normal which leads to arthritis of the knee joint. An ACL tear is one of the commonest serious injuries in sport - for example, in the AFL, 12% of all matches missed due to injury are from ACL tears. 2. How are ACL tears diagnosed? Most ACL tears can be detected by experienced examiners as the knee joint will undergo abnormal movements when stressed. There is a variation in the normal range of these tests so the amount of movement is compared to the other knee. Sometimes these tests can be inconclusive immediately after an injury, due to excessive swelling. If clinical testing is inconclusive and it is very important to know at an early stage whether the ACL is torn, a special test called an MRI (Magnetic Resonance Imaging) Scan can be performed, although these are costly and are not covered by Medicare or health insurance. Standard X-rays will show fractures but do not show ACL tears. 3. If my ACL is torn, should I have surgery to repair it? As a general rule, the body cannot repair a torn ACL if the tear is complete. Partial tears may sometimes heal but often will progress to becoming complete tears. If surgery is needed, the surgeon will not repair the ligament directly, as this has a low success rate, but will instead use a nearby tendon to reconstruct the original ligament. The answer to whether you should have surgery depends on a combination of three factors: (1) Your future demands in multi-directional sport. For example, a professional football player would be strongly advised to have an ACL reconstruction whereas a 50 year old sedentary person would not. (2) The amount of instability in the knee. A knee that has strongly positive features of ACL instability on examination or is giving way on daily activities will almost certainly require surgery, but a knee that is relatively stable on sporting activities (the minority of ACL tears) may survive without surgery. (3) Your acceptance of the costs of surgery. An ACL reconstruction and associated costs can be expensive, even with full private health insurance. However, the long term costs, both monetary and lifestyle, of having a degenerative knee joint are very steep. If a reconstruction is done for the right reasons, it is money well spent. 4. What is the success rate of the surgery? The ACL is the most commonly reconstructed ligament in the body, although the surgical techniques to perform this operation have only been developed over the last 20 years. Experienced knee surgeons will claim a success rate for this operation of 85-90%. However, success should only be judged by the long-term stability and lack of pain in a knee. Because it is very difficult to follow patients over a long period of time and also that virtually every surgeon uses a different technique, the exact success rates for various surgeons are not known. Most failures involve reinjury to the structures in the knee. General complications such as infection and venous thrombosis after surgery can occur but are not very common. 5. Are the differences in technique important? The answer is yes, but it is difficult to make accurate statements about the success rates of various surgical techniques. Most doctors would agree that ACL reconstruction surgery is very technically demanding and would recommend a surgeon who has successfully returned top level athletes to their sport. Therefore, the odds of a successful outcome may be less if the operation was performed by an inexperienced surgeon in a public hospital. One major difference in technique between experienced surgeons is in choice of tissue to replace the ligament. Some surgeons use a segment of the patella tendon from the front of the knee, whereas others use a combination of hamstring tendons from the inside of the back of the knee. It is not well established that either technique is universally better than the other. 6. Is one type of reconstruction stronger than the other? This is not conclusively proven, although evidence from studies in which the different types of reconstructions are compared generally favours the patella tendon technique. A recent randomised control trial in the American Journal of Sports Medicine found the patellar tendon technique to result in a more stable knee. The theory as to why the reconstruction may be stronger is that the patellar tendon is connected to bone at either end, it can be fixed inside the knee (bone fixed to bone) more firmly than the hamstring tendons (tendon fixed to bone). However, the thickness of the patellar and hamstring tendons themselves, which are obviously important for strength of the graft, also vary significantly between individuals, so it may not be the case in all individuals that the patellar tendon reconstruction is stronger. 7. Are there more side effects from one type of reconstruction? The site of graft tissue taken can give rise to symptoms, either in the patella tendon or hamstrings, although these are generally more significant with the patella tendon. Side effects such as pain on kneeling and squatting appear to be more common with the patella tendon technique. A basketball player, who was prone to patellar tendonitis, might be better advised to have a hamstring tendon reconstruction, for example. A rugby league player who had a history of hamstring tears may be better advised to have a patellar tendon reconstruction. In general, the pain, length of hospital stay and size of scar are all less with the hamstring tendon technique. 8 . How can I decide whether a hamstring or patella tendon reconstruction would be better for me? Who will make the decision? The decision will be made by the surgeon and surgeons usually will have a preferred technique which they will recommend to most people based on their experience. Some surgeons will offer both techniques and will choose differently for different individuals (e.g. professional football players – patellar tendon for reasons of graft strength, sedentary occasional athletes – hamstring tendon for reasons of minimal side effects of surgery). If after discussing the positives and negatives you have a preference for one technique over the other, you can ask for a referral to a surgeon who specialises in that technique. For further information: Evidence base for ACL reconstruction, Dr J, Sport Health 2006 Autumn 24(1). 9. Can ACL tears or recurrences be prevented? ACL injury is associated with multidirectional sport (football, basketball, netball and skiing particularly), so refraining from these sports is a way to prevent injury, but often not acceptable to athletes. The mechanism of injury is often getting the foot caught in the ground while the body moves in another direction. In football, wearing boots with shorter stops helps prevent the foot getting caught in the turf. In all sports, a stabilising knee brace may offer some protection. However, there is no sure way to prevent these injuries occurring in these sports. To post a comment or ask a question about these injuries, visit the injuryupdate Forum, click here .
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