Anterior Cruciate Ligament (ACL) Injuries

The anterior cruciate ligament (ACL) is the primary restraint that limits how far the tibia (shin bone) slides forward in relation to the femur (thigh bone). When the ACL tears and that restraint disappears, the knee becomes unstable and may unpredictably buckle or give way. An ACL tear is a common knee injury in football and basketball.

The ACL may tear suddenly and without warning when an individual decelerates, cuts to the side, or lands awkwardly. Symptoms of a torn ACL include an audible “pop” at the moment of injury, and the slippage of the knee out of its joint, accompanied by severe swelling and painful movement.

Diagnosis

The best time to diagnose an acute ACL tear is within the first hour after injury, before the knee swells, but this is not always possible. The initial evaluation includes a complete history of the injury — how it happened, whether the knee was hyperextended or other aspects of the “mechanism” of injury, whether the individual heard a pop, where and how badly the knee hurts, and whether the knee feels unstable — as well as details of previous knee injuries.

Once a thorough history is obtained, the physician performs a physical exam of the knee to assess the stability of the ligaments. Using specific tests, the physician can diagnose ACL injuries by applying forces to the knee and feeling for abnormal motion. Obtaining additional studies, such as x-rays and an MRI, can be very helpful to give an accurate picture of the extent of the injury.

Treatment

Treatment may be nonsurgical or surgical, depending on the patient’s desired lifestyle. The question is not so much the patient’s level of activity in the past, but the expectations for the future. If a patient’s goal is to continue an active lifestyle, surgery may be the treatment of choice because a torn ACL does not heal.

Nonsurgical therapy consists of a period of protective bracing with progressive return to range of motion and muscle-strengthening exercises. The goal is to create natural stability for the knee by developing the quadriceps and hamstring muscles.

Prevention

Several prevention programs have been developed in an attempt to decrease the incidence of ACL injuries. The focus of current prevention programs is on proper nerve and muscle control of the knee. These programs focus on plyometrics, balance, and strengthening and stability exercises for the lower limbs.

Rehabilitation

The goals of rehabilitation are to restore range of motion and to strengthen the quadriceps and hamstring muscles, which help stabilize the knee. Precautions you can take at home for minor ACL injuries include:

• Reduce activity during the acute phase.
• Ice the injury multiple times per day.
• Compress the knee with a bandage or wrap.
• Elevate the knee above the level of the heart.
• Use anti-inflammatory medications such as ibuprofen to reduce inflammation and speed up recovery.

Rehabilitation Exercises

• Quad sets: Sit with legs extended and fully contract the muscles of the front thighs. Hold contractions for 10 seconds. Repeat 10 times for three sets.
• Straight leg raises (hip flexion): Lie with one leg extended and the other bent at the knee. Lift the entire leg from the hip so that the heel is about five inches above the floor. Hold this position for five to 10 seconds and then slowly lower the leg. Repeat 10 times for three sets.
• Backward leg raise (hip extension): Lie on stomach with legs straight. Lift one leg as high as possible and hold for five to 10 seconds and then slowly lower the leg. Repeat 10 times for three sets.
• Hip abduction: Lie on side of uninjured leg, so that the injured leg is on top of the uninjured leg. Lift the injured leg at the hip away from the body. Lift the leg as high as possible and hold for five to 10 seconds, then slowly lower the leg. Repeat 10 times for three sets.
• Hip adduction: Lie on side of injured leg, with uninjured leg bent at the knee and foot flat on the floor. Lift the injured leg at the hip toward the other leg. Hold for five to 10 seconds and then slowly lower the leg. Repeat 10 times for three sets.
• Half-knee bends: Stand with feet shoulder-width apart. Slowly lower the body weight by bending the knees. Do not perform a full squat, but rather stop at about half of the full squat position and then fully extend the knees. If there is pain before achieving the half-squat position, stop downward travel at that point. Repeat 10 times for three sets.