Common mechanism for a contact related injury of the ACL is twisting on a bent knee and it is usually accompanied with a popping or snapping sound. The mechanism for a non-contact injury involves a straight knee and excessive rotation. The injury is usually associated with immediate high levels of pain and swelling. There is often a feeling of instability or “giving way” if you are able to stand on the leg at all. The injury is often accompanied with associated tears of other ligaments e.g. medial collateral ligament or the menisci of the knee. This ligament is important for stability and if it is not present, it is difficult to run or play sport because of the new feeling of weakness in the knee.
How is it Managed?
If the tear is incomplete, a surgeon may opt to manage the knee conservatively using a brace for protection in the hope that the ligament will regenerate and heal itself. Complete tears usually need surgical intervention, especially if the individual wishes to return to sport. The ACL is repaired using a graft from either the patellar tendon or the hamstring tendon (using the tendons of the muscles gracilis and semitendinosus). In the past few years the trend has been for surgeons to use more hamstring tendons but many do still use a patellar tendon graft. Each method has its benefits and also some problems that need to be addressed by the physiotherapist whom you have been referred to.
What Does the Operation Involve?
The surgery is usually performed via arthroscopy, which means that the incision is very small. This factor should help reduce the amount of pain and swelling after the operation. The damaged ACL is replaced using either a previously harvested patellar tendon or hamstring tendon. Hamstring tendons are usually doubled so that four strands of tendon are used and this gives the graft the potential to be even stronger than your original ligament once it has healed itself into your knee. The new ACL is inserted into a tunnel which the surgeon has drilled through the knee joint and the new graft is adjusted to give a good amount of tension. Locking screws are used to hold the graft tightly in place. The screws used usually dissolve within months once the graft has healed.
What is the Recovery Time?
It takes 6-10 weeks for the graft to generate its own blood supply and until this time it is especially vulnerable to re-injury. It is important that you follow only the set exercise program given to you by your physiotherapist. Recovery must be set at a very slow pace to ensure that the graft has enough time to heal and become as strong as a normal ligament. The graft will take anywhere from 9-12 months to completely heal. Some elite sportsmen, such as AFL footballers, that undergo intense physiotherapy begin sport again after 9-10 months but the recommended time period is after about 12 months. Other activities however such as beach walking and riding may be begun much sooner but again, only as recommended.
What Else Can I Do?
Upper limb exercises are an excellent way to maintain fitness and upper body strength whilst in recovery.
Post operatively there will be considerable swelling around your knee. Swelling can be reduced by:
- Wearing a tubigrip sock around your knee during the day
- Keeping your leg elevated above your heart as much as possible
- Using ice on the knee for 20 minutes at a time (especially if the knee becomes hot and swollen after doing your exercises.)
- Make sure waterproof dressing remains intact and wound is kept dry.
Follow post op instructions.
Swelling control, Full knee straightening, begin exercise program.
Driving at 6 weeks minimum, walking for fitness on flat ground, swimming with no kick, return to work with modified activities, stationary cycling.
Power walking, water running, road cycling, gardening.
Knee Strength Test usually performed and then running is begun.
Running and Hopping Test usually performed and then can return to gentle training in your sport with no contact, full work duties, sprints.
Preparation for full return to sport and full training.