Frequently Asked Questions: ACL Injuries

What is the ACL?

The ACL, or the Anterior Cruciate Ligament, is one of four main ligaments around the knee that connect the femur (thigh bone) to the tibia (shin bone). The ACL prevents the tibia from sliding forward on the femur, and provides stability to the knee with twisting or pivoting activities, such as playing basketball and soccer.   

Illustration of the anterior cruciate ligament (ACL)

Illustration copyright 2000 Nucleus Communications, Inc. All rights reserved.

What Causes a Torn ACL?

The ACL is generally torn by twisting the knee due to pivoting, sidestepping, or cutting combined with deceleration. Usually, there is no contact with another player or person. The ACL is one of the most commonly injured ligaments of the knee. It is estimated that 200,000 ACL tears occur annually in the United States with 100,000 ACL reconstructive surgeries performed each year. Approximately half of the time, other injuries occur along with the torn ACL, such as torn cartilage (meniscus) or other ligament injuries.

How will a torn ACL affect the function of my knee?

With the initial injury, patients often fear or feel a “pop” with a sudden onset of pain and inability to return to sports. Sometimes it will be difficult to walk; often there is gradual swelling and stiffness in the knee. The torn ACL will allow the knee to “buckle” or “give out” with certain pivoting or cutting activities. Sometimes the problem can become so severe that even a simple activity like walking or working around the house will cause instability episodes.

Who should I see for my knee problem?

A severe knee injury requires medical attention to decrease the chance of further damage. Orthopaedic surgeons, like the ones at POA, specialize in the care of injured ligaments, bones, tendons and joints. They deal with sports medicine injuries on a daily basis. Your primary care physician also can be an excellent resource for this type of injury. Find a Sports Medicine specialist.

Should I have an MRI?

Initially, your physician will want to examine your knee to check for range of motion and stability. X-rays are generally taken to rule out a fracture or other problem. An MRI is an excellent tool to look at the ACL without having to perform surgery. It can show damage to other areas of the knee, such as cartilage and other ligaments. Sometimes, your physician will be able to diagnose your knee from his or her office examination and X-rays, without needing an MRI.

Should I have surgery?

The decision to have surgery to repair a torn ACL depends on your age, activity level, degree of instability and associated injuries. Some people are able to get back to full activities without surgery just by strengthening the surrounding muscles. Many people find that their activity level is decreased because of the torn ACL and desire reconstructive to allow them to return to full activities. In most instances, surgery is successful and will allow full return to activities of all levels. Reconstructing the torn ACL can also help prevent further damage to the knee from chronic injury.

What exactly is performed during surgery?

The torn ACL cannot be sewn back together. Instead, a tendon is substituted for the ACL ligament. This can either be a piece of patellar tendon or hamstring from your body, or a piece of donor tissue. Once the tendon is harvested, it is attached to two long sutures and pulled into place through small holes that the surgeon will make in the knee. It is held in place with two screws while the holes in the bone heal. The screws are normally made of calcium absorbed by the body over time. Once the surgeon decides the knee is sufficiently stable, the knee is closed and dressed.

Will I spend the night in the hospital?

Most of the time, ACL repair is performed in an outpatient setting.

Will it be painful?

Multiple techniques are available to decrease the likelihood of severe pain following surgery. Your anesthesiologist may use a nerve block before surgery to lessen the likelihood of pain during and after the procedure. Pain medicine also is available, and early exercise will help decrease pain.

Will I be on crutches or need a brace after surgery?

Initially, you will be on crutches for approximately seven to ten days after surgery. You may need a brace for a few weeks afterward to help provide stability while your muscle strength gradually returns.

Will I need physical therapy?

Physical therapy is an essential part of the treatment of a torn ACL. You will have your first physical therapy session within a day or two of your surgery. Early, appropriately aggressive therapy is one way you can return to full function quickly, and it also decreases the chance of complications after surgery.
Initially, you will start with range of motion exercises with gradual strengthening as the pain and swelling decrease and healing occurs. Eventually, you progress back to full activities and can return to sports.

What is the prognosis?

Full recovery to all activities prior to injury is seen in most cases. Individuals are generally able to return to all sports at all levels after successful ACL reconstruction.