What is the ACL ?

If you have not yet reviewed the general knee anatomy page, please do so now. The ACL (Anterior Cruciate Ligament)is one of the four stabalizing ligaments of the knee. It keeps the tibia from moving too far forward in relation to the femur.

How is the ACL injured?

The ACL is the most commonly injured ligament in the knee. This is the first ligament that becomes tight when the knee is straightened. If the knee is forced to straighten more than it should or hyperextended, the ACL can tear. If the tibia moves too far forward the ACL can also tear. These kind of actions occur most frequently in sports where one part of the leg stays stationary while the rest of the body changes direction rapidly, such as basketball, football and downhill skiing. If a twisting of the knee is followed by a loud popping noise and a feeling of instability in the joint, you've probably torn your ACL.

What are the symptoms of an ACL tear?

As with any injury, the symptoms of an ACL tear vary from person to person. As stated above, when the ACL is torn, you will be able to feel or hear a "pop" in the knee, followed by swelling and joint instability (inability to put much weight on that knee) and/or a feeling that the knee wants to "give way". If the injury is not treated, the swelling will usually be gone after a few weeks, but the instability will remain. It is important that you see a physician if you have any of these symptoms, long term knee instability can lead to early arthritis of the knee.

How is an ACL tear diagnosed?

Swelling within a couple of hours of a knee injury is usually a good indicator of a torn ligament. An ACL tear is best diagnosed by a physical examination by an orthopedist. If the orthopedist suspects an ACL tear, he will usually confirm that diagnosis with an MRI scan. He may also take X-rays to ensure that no bones have been injured.

How is an ACL tear treated?

Regardless of whether the ACL is torn or simply stretched, it will no longer properly support the knee. Chances are your orthopedist will want to reconstruct the ligament. This will help to prevent further injury as and arthritis in the future. If the ligament is only stretched or partially torn, the patient may choose to undergo physical therapy rather than surgery. However, without reconstruction the knee may not regain full stablity.

What is ACL reconstruction?

In order to reconstruct your ACL, your orthopedic surgeon will remove the old, torn ligament and other loose tissue in the joint to prepare for the new ligament (the graft). The ligament can be reconstructed in several ways. Usually the surgeon will take part of the patellar tendon or part of the tendon from one of the hamstring muscles (usually from the semitendinosus muscle). The surgeon will fold the and sew the tendon until it is the proper size to replace your torn ACL and will then put it in place, usually with one screw on each end. Another option for the reconstructed ligament is to use an allograft (donor tissue from a cadaver.) Reconstructed ligaments are generally much stronger than the original ligament.

What happens after surgery?

You will most likely stay the night at the hospital to make sure everything goes well after surgery. Depending on what exactly was done during your surgery, you can expect to have 3-6 incisions around the knee joint. You will have to use crutches and wear a brace until your doctor tells you that you're ready to start bearing weight on your knee. There will be some swelling and bruising, but this will go away as the knee starts to heal. Your doctor will prescribe physical therapy to get your knee back to it's normal range of motion and strength. Recovery from an ACL reconstruction takes some time, but as long as strengthing exercises are done on a regular basis, you should be able to return to work within 6 weeks and return to normal activity within 6 months. Remember however that all people are individuals and recovery time will be different for each person.

Other ACL associated injuries

There are two other injuries commonly associated with ACL tears. These are Meniscus Tears and Collateral Ligament (MCL & LCL) tears. If your orthopedist suspects an ACL tear, he will also look at these structures to make sure they are not injured.