Disruption of the anterior cruciate ligament is one of the more common knee injuries seen,
particularly in running twisting sports such as football and netball. The patient will often experience a popping sensation at the time of the injury. It commonly occurs after a player is tackled, or lands awkwardly from a jumping position. It is shortly followed by acute pain and swelling of the knee. The latter is due to internal bleeding into the knee joint (haemarthrosis). The patient will often be significantly disabled and have difficulty walking for several days. Whilst these acute symptoms will eventually resolve spontaneously, a feeling of insecurity as well as of recurrent giving way often occur when the patient tries to return to their sporting activity.
The Anterior Cruciate Ligament or ACL, is situated in the centre of the knee and is one of the most important stabilising ligaments of the knee. Once it has ruptured it has little capacity to heal and frequently leads to a feeling of giving way or instability of the knee. Some patients with this injury can manage quite well with conservative management, particularly if they alter their level of sporting activity.
However, for the majority of patients, especially those wishing to continue with running twisting sports, a knee reconstruction is recommended. An anterior cruciate ligament reconstruction shouldbe considered when patients develop recurrent symptoms of giving way of the knee or those who wish to return to running/twisting sports.
This procedure involves replacing the ACL with new tissue taken from adjacent ligaments or tendons around the knee. This tissue is called the ACL graft. The most common sources of the ACL graft are the middle third of the patella ligament or the inside hamstring tendons. The results of both hamstring and patella ligament grafts have been compared in literature and both produce very satisfactory results in the vast majority of patients, with little difference in the overall function. The hamstring graft does carry some minor advantages including:
- less quadriceps weakness
- less kneeling pain postoperatively
- hamstring tendons in some cases will regenerate themselves
The procedure is carried out with the assistance of the arthroscope and is done through three small incisions over the front of the knee. The rest of the knee can be expected at the same time. Any damage to the surface of the joint can be treated, as well as managing any associated cartilage (meniscal tears). Sometimes this involves either removing or repairing the damaged meniscus. The procedure takes approximately 1 hour.
An ice pack will be placed around the knee initially postoperatively to reduce pain and swelling which should be continued intermittently for the first 48 hours. The patient will be allowed to get up the following day on crutches and this will be done with the assistance of a physiotherapist. The physiotherapist will give you some simple exercises to do which will include straight leg raising exercises as well as knee bending. It is important to try and take as much weight on the leg as soon as comfortable to reduce the risk of quadriceps wasting as well as deep venous thrombosis. Braces are usually not required but will occasionally be used if a meniscal repair is performed or if there is significant collateral ligament damage. Most patients are discharged home within 1 to 2 days of surgery and crutches are usually only required for 2 weeks duration.
The patients will usually be reviewed at 2 weeks postoperatively where further instructions will be given. It is usually recommended that the patient sees a physiotherapist at this stage for ongoing rehabilitation. Exercises including using an exercise bike and/or swimming is encouraged once the wounds are well healed. The ACL graft takes some weeks to regain a blood supply and several months to regain its strength. It is therefore not usually recommended that one return to contact or running/twisting sports until 10 to 12 months postoperatively.
Advances in technology and refining techniques have dramatically improved the results of ACL reconstruction. The vast majority of the patients can expect to return to their pre-injury sports, however, it needs to be kept in mind that with any major surgical procedure there are complications that may affect the long term result. Approximately 6 out of every 100 patients will develop recurrent instability of the knee due to stretching or re-rupture of the ACL graft.
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