Chronic ACL Deficiency

An anterior cruciate ligament (ACL) injury can involve:

• A small or medium tear of the ligament.
• A complete tear of the ligament (rupture).
• A separation of the ligament from the upper or lower leg bone. This is called an avulsion.
• A separation of the ligament and part of the bone from the rest of the bone. This is called an avulsion fracture.

When any of these occur, the lower leg bone may move abnormally on the upper bone. It may feel like the knee is giving out.

An ACL injury may develop into a long-lasting problem called chronic ACL deficiency. How well the ACL can control knee movement decreases, and this causes more sliding of the bones. The knee becomes more and more unstable. It starts to buckle or give out, sometimes with pain and swelling. This can cause further injury, loss of strength (weakness), and instability. This abnormal knee motion also can damage cartilage and trap and damage the pads that cushion the knee joints (menisci). It also can lead to premature osteoarthritis.

ACL surgery is often done for chronic ACL deficiency, unless the knee is so damaged that surgery won't help. When possible, starting a rehabilitation (rehab) program before surgery can help speed rehab after surgery.

If you have chronic ACL deficiency and you are willing and able to stop doing things that require a lot of knee stability, rehab may make your knee stable enough to do daily activities. You may not need surgery.