Question:

Recently many athletes have been tering their ACL in their knee. Can you give me some information on this topic?

Answer:

The anterior cruciate ligament, or ACL, is a tough band of tissue connecting the femur (thigh bone) to the tibia (leg bone). Specifically, it functions to prevent forward movement of the tibia from beneath the femur, or similarly, backward movement of the femur over the tibia. Also, it serves to resist rotational and sideways forces to the knee. Although a contact injury (direct blow to the knee) can certainly tear the ACL, usually it becomes torn in a “non-contact” fashion, such as when a person is running and then suddenly stops and twists the knee. ACL tears are quite often accompanied by injuries to additional knee structures, most often one of the menisci (knee cartilages), and/or the medial collateral ligament (along the inner side of the knee). In general, the more structures injured, the worse the injury and the longer the recovery period. ACL injuries are very common knee injuries, so if you hear that a person has “torn a ligament” in their knee, it`s usually the ACL, especially if there`s been no direct trauma (or perhaps the MCL, or medial collateral ligament, if there has been direct trauma).

ACL injuries, by themselves, also vary in severity, and thus, can be mild, moderate, or severe (Grades 1, 2, or 3). Grade 1 is microscopic tearing of ligament fibers without any slackening or loosening of the ACL. Grade 2 is more severe tearing of fibers with resultant looseness or laxity of the ACL and therefore more “play” or relative motion between the tibia and femur. Grade 3 is complete disruption of the ACL, with a greater degree of knee instability or “giving out” episodes than with Grade 2 injuries (realize the knee is still held together by other ligaments, as well as by the muscles and tendons which cross it).

Someone who sustains an isolated ACL injury typically feels a pop or snap in their knee, from a non-contact mechanism of injury, followed by a significant amount of swelling within a few hours after the injury. It is usually difficult for this person to continue participating in whatever activity they were doing, and usually difficult to even put any weight on that leg.

ACL injuries do not heal or tighten up on their own. These are often treated with surgery, but don`t always need to be. A person who`s had a Grade 1 ACL injury and has not also injured their meniscal cartilage may go on to regain full function without surgery. At the other extreme, someone who has sustained a Grade 3 ACL injury along with a meniscus tear will most often undergo surgery. The more physically active and the younger someone who`s torn their ACL is, along with the more “unstable” their knee is (giving way unpredictably), the more likely they would be to benefit from surgery. On the other hand, the older and more sedentary a person is, the less likely they`d be to undergo surgery.

The treatment for any ACL injury includes RICE – Rest, Ice, Compression, and Elevation. It also includes bearing weight, usually with the assistance of crutches at first, only as tolerated by pain. Of great importance is progressive strengthening of the person`s thigh muscles, especially the hamstring muscles in back of the thigh, but also the quadriceps muscles in the front part of the thigh. Then, depending on the severity of the injury (Grade) as well as the person`s age and activity level, the person may go on to wear a brace to provide a means of externally stabilizing their knee, which has less internal stability since the ACL was torn. Bracing can be done without surgery, as a means to assist deciding whether or not to proceed with surgery, and is also used after surgery, often once the postoperative cast is removed. Following surgery, the person may continue to wear a brace for a year or more, especially during activities requiring cutting, quick stops and starts, or potential contact with another player, all of which could re-tear the reconstructed ACL.

If surgery is decided on, it is preferred to not do this right away, but to wait a few weeks, to allow the inflammation and swelling from the acute injury to calm down a bit. Although there are many surgical procedures, the usual one involves taking the middle third of the tendon which goes from the lower part of the patella (kneecap) to the tibia, and then placing this tendon segment in the same postion as was the ACL before it became torn. This tendon graft may then be anchored into place with a screw into both the tibia and femur. If a peson who has torn their ACL does not undergo surgery, but remains very active and experiences repeated episodes where their knee gives out on them and swells, their risk for developing arthritis in that knee increases with every such episode which occurs. On the other hand, the risk for arthritis is reduced when a person can modify their activities to minimize the number of such knee giving-way and swelling episodes.

For more information:

Go to the Sports Medicine health topic.