Anterior Cruciate Ligament (ACL) Injury

Anterior Cruciate Ligament (ACL) Injury

What is it?
Anterior cruciate ligament (ACL) injury is the most common knee injuring, resulting from a stretch or tear in the ligament. Ligaments are strong bands of tissue that connect one bone to another. The ACL is one of the major ligaments in the knee, connecting the thigh bone (femur) to the shin bone (tibia). It helps to keep the knee stable and protects the femur from sliding or turning on the tibia.
Who gets it?
While anyone can injure an ACL, it is unusual in childhood. The incidence of ACL injury peaks in adults during their middle years.
What causes it?
ACL injuries most often result from sports where the foot is planted on the ground while the leg is being twisted, such as in football, soccer, basketball and skiing. The ACL may also become injured when the knee is straightened further than it normal (hyperextended). It can also occur when the thigh bone is forcefully pushed across the shin bone, such as with a sudden stop while running or a sudden transfer of weight such as in skiing.
A chronic ACL injury is often the result of an injury in which the patient either did not consult a doctor after initial injury, the diagnosis was missed, or nonoperate care of an ACL injury was unsuccessful.
What are the symptoms?
Often the patient will hear a popping sound when the ACL injury occurs and will not be able to continue the activity. Swelling of the knee within the first several hours of injury will usually follow.
In the case of a chronic ACL injury, the patient will sometimes experience increasing instability of the knee during twisting and pivoting movements and muscle weakness.
How is it diagnosed?
A doctor may suspect an ACL injury after noticing the knee is loose and swelling is present upon initial examination. To confirm diagnosis, the doctor may draw blood from the knee for testing and order x-rays to be taken to see if there is an injury to the bones in the knee. An MRI test may be done to show the condition of the ACL.
The doctor may also examine the ligament, lateral ligament and posterior cruciate ligament for injury, and may make a comparison of the injured and uninjured knee to make sure that another injury is not overlooked.
In a chronic ACL injury, the longer the injury has been present the more likely it is to have an abnormal appearance on MRI examination. The doctor should also determine if there is an associated instability from other tears.
What is the Treatment?
Initial treatment for an ACL injury may including icing the knee, keeping the knee elevated whenever possible and administering anti-inflammatory medications.
Long-term treatment for ACL injuries may vary for each patient. Activity level, age, job demands, and general medical condition may be factors in the decision to recommend reconstruction. If the knee "gives way" during daily activities, this is a strong indication for surgery to prevent injuries from falls.
Since a torn ACL will not heal by itself, reconstructions by using ligaments or tendons from another part of the body (graft) are used. During ACL reconstruction, holes are drilled in the femur and tibia, and the torn ACL is removed. The graft is passed through the drill holes to replace the ACL, and is anchored in place using screws or staples. The hope is that stabilized knees will allow patients to return to pre-injury activity level and prevent further damage to the knee.
New surgical equipment has made this operation easier to perform and more precise, so that more surgeons are able to perform it. Patients with a chronic ACL injury and recurrent giving way of the knee are also candidates for ACL reconstruction.
Self-care tips
With successful ACL reconstruction, the patient may expect to return to vigorous sporting activities and degenerative changes will be prevented. Current rehabilitation after ACL reconstruction includes achieving full motion very quickly after reconstructive surgery. Exercises such as the leg press, bicycling and stair-climbing machines are usually recommended during rehabilitation.

This information has been designed as a comprehensive and quick reference guide written by our health care reviewers.  The health information written by our authors is intended to be a supplement to the care provided by your physician.  It is not intended nor implied to be a substitute for professional medical advice.