Its description, causes, symptoms, diagnosis and treatment (operative and non-operative)
The anterior cruciate ligament (ACL) is the main stabilizing ligament on the inside of the knee. Its main function is to prevent the tibia (shin bone) from sliding forward and rotating on the femur (thigh bone). Tears/ruptures of the ligament result in knee instability.
What are the causes?
ACL tears are typically caused by twisting or hyperextension injuries. Sports activity like pivoting or sudden deceleration when running and falls during skiing are considered non-contact causes of ACL tears. Direct trauma to the back or side of the knee during collision sports is considered a contact injury to the ACL.
What are the symptoms?
ACL tears cause immediate pain and often swelling. You may feel something “pop” inside the knee. An initial inability to bear weight on the leg may subside and walking may be possible after several minutes. The knee may feel loose or that it is going to “give out” and return to sport is impossible. Over time, swelling will increase and motion may be lost.
How is it diagnosed?
Your surgeon will perform a thorough history and physical exam with X-rays. On exam, swelling and loss of motion and strength is present. Your surgeon will perform maneuvers to check stability of all the knee ligaments and the meniscus. An MRI is helpful to confirm the diagnosis, showing the ACL tear. The type of tear (partial, complete, avulsion from either the tibia or femur) can be defined, which may assist in surgical planning. The MRI may also show bone bruising secondary to the injury.
How is it treated?
Non-operative - ACL tears do not heal. Some patients elect not to have reconstruction surgery. Non-operative treatment increases the risk of “wear and tear” arthritis and meniscus tears because of the instability in the joint. Non-operative treatment consisting of anti-inflammatory medication, physical therapy, cryotherapy and activity modification may be prescribed prior to surgery to decrease the swelling, regain motion and strength, as research has demonstrated that surgery is less complicated and patients have better outcomes. Non-operative treatment in surgical patient may be skipped if other injuries to the meniscus and cartilage are present and need to be repaired immediately.
Operative - Operative management of ACL tears depends on the type of tear. ACL repair may be indicated in patients where the ACL is clearly torn off the wall of the femur (thigh bone) or tibia (shin bone. ACL repair is accomplished through a minimally-invasive arthroscopic procedure and sewed back into place and fixed with screws or buttons. The repair may also be supplemented with high-strength suture.
If formal reconstruction is required, a new ACL graft will be fixed in place of the original ligament. A technique for graft placement and graft choice is a shared decision between you and your surgeon. Most techniques are performed through a minimally-invasive arthroscopic procedure. The graft can be taken from around your knee or from a donor. Postoperative rehabilitation, return to daily activities and return to sport depends on the technique and graft chosen, and is at your surgeon’s discretion.