The ACL prevents the shinbone from sliding forwards beneath the thighbone. The ACL can be injured in several ways:
- Changing direction rapidly
- Slowing down when running
- Landing from a jump
- Direct contact, such as in a football tackle
Recognizing an ACL injury
If you injure your ACL, you may not feel any pain immediately. However, you might hear a popping noise and feel your knee give out from under you. Within 2 to 12 hours, the knee will swell, and you will feel pain when you try to stand. Apply ice to control swelling and elevate your knee until you can see an orthopaedic surgeon.
If you walk or run on an injured ACL, you can damage the cushioning cartilage in the knee. For example, you may plant the foot and turn the body to pivot, only to have the shinbone stay in place as the thighbone above it moves with the body.
Diagnosing an ACL injury
A diagnosis of ACL injury is based on a thorough physical examination of the knee. The exam may include several tests to see if the knee stays in the proper position when pressure is applied from different directions. Your orthopaedist may order an X-ray and MRI (magnetic resonance imaging) or, in some cases, arthroscopic inspection.
A partial tear of the ACL may or may not require surgical treatment. A complete tear is more serious. Complete tears, especially in younger athletes, may require ACL reconstruction.
Treating ACL tears
Both nonoperative and operative treatment choices are available.
- May be used because of a patient's age or overall low activity level.
- May be recommended if the overall stability of the knee seems good.
- Involves a treatment program of muscle strengthening, often with the use of a brace to provide stability.
Operative treatment (either arthroscopic or open surgery):
- Uses a strip of tendon, usually taken from the patient's knee (patellar tendon) or hamstring muscle, that is passed through the inside of the joint and secured to the thighbone and shinbone.
- Is followed by an exercise and rehabilitation program to strengthen the muscles and restore full joint mobility.