Dear Doctors: I twisted my knee snowboarding. I thought it was just a sprain, but it turns out I have a partial tear in my ACL. My doctor says I need surgery. If I just wait and am very careful, won't it eventually heal by itself?
Dear Reader: The anterior cruciate ligament, or ACL, is one of the four major ligaments in the knee, which is the largest joint in the body. For those who aren't familiar, ligaments are strong, fibrous strands of connective tissue that attach a bone to another bone. The ACL weaves through the middle of the knee and helps link the femur, or thigh bone, to the tibia, the larger of the two bones that make up the shin.
The knee is a hinge joint. Its structure allows about 130 degrees of back-and-forth movement along a flat plane. The ligaments that hold the bones of the knee joint together also provide stability and help limit rotational movement.
Although they are quite strong, ligaments are not elastic. As a result, when lateral force is applied to the knee, as happens when you twist it or get bumped or tackled from the side, the ligaments are susceptible to damage. Depending on the degree of force and the position of the knee at the time, they can be stretched, sprained, partially or completely torn, or separated from the bone. Diagnosis is via a physical exam of the knee and often an X-ray to check for bone injury.
When the ACL is stretched, strained or undergoes a very minor tear, nonsurgical treatment can be an option. This typically includes rest, the use of a knee brace to provide stability and progressive physical therapy. The challenge is that ligaments have a limited blood supply, and as a result, they are slow to heal. The recovery period for nonsurgical treatment of a sprained or strained ACL or a small tear is measured in months.
When the ACL has a significant tear, a surgical repair is often the best option. It depends on the degree of injury and the type of activities the patient engages in. When the ligament has been pulled off the bone or is completely torn in half, the knee becomes extremely unstable. This makes standing or walking both painful and difficult and leaves all of the structures of the knee susceptible to further injury.
In those cases, a surgical repair is required. This typically entails the use of a graft, either harvested from another part of the body or from a tissue donor, to replace the damaged ACL.
When deciding on treatment, the person's activity level is an important consideration. Active adults, particularly those who take part in sports or whose work or lifestyle is hard on the knees, often find surgery to be the best option. Surgery lasts about two hours, and you usually go home the same day.
Recovery involves the use of a brace and crutches, as well as physical therapy. After they have recovered, some patients find it helpful to continue to use a knee brace during physical activity.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
