The anterior cruciate ligament (ACL) is one of four main ligaments in the knee. It helps provide stability to our knee. It is one of the more common non-contact athletic knee injuries. ACL tears are more common in females than males. ACL tears are most commonly treated with ligament reconstruction surgery. After reconstruction surgery, patients will go through a course of rehabilitation that will focus on motion, strength, and function of the knee. The process can take 9-12 months, before the patient is ready to return to sports activities.
The ACL resides inside the joint capsule of the knee. It connects the femur (thigh bone) to the tibia (shin bone). Its main purpose is to prevent anterior and rotational motions of the tibia, our shin bone. Other structures of the knee can also be involved when there is an ACL injury - our medial collateral ligament, meniscus, or cartilage are also commonly involved with primary ACL injuries.
ACL tears are most often non-contact injuries, meaning they are injured without an external force to the knee. Usually they occur with landing, cutting, or pivoting movements when the involved foot is planted. When an individual tears their ACL, their knee often rotates inward relative to the planted foot. It is common to hear or feel a pop. Because of lack of contact, poor neuromuscular control or body mechanics are thought to be a primary and modifiable risk factor with ACL injuries. There are other common risk factors such as participation in cutting sports, being female, and previous injury to an ACL.
Common symptoms after an ACL tear are pain, swelling, loss of motion, instability or buckling of the knee, and weakness in the quadriceps muscle. People will often complain of instability with the knee limiting their ability to perform daily activities.
A thorough physical exam should be able to identify an ACL tear; however, an MRI is often utilized as the gold standard in diagnosis.
The most common treatment for athletes and individuals who suffer from instability after ACL tear is ligament reconstruction. Often before surgery it is common to do some work with physical therapy to make sure the patient has full motion, no swelling, and good strength. This has been found to improve postoperative outcomes when compared to going immediately into surgery after injury.
Reconstructive surgery utilizes a graft to replace the damaged ACL. The remnants of the injured ligament are removed and a new graft is implanted. Most commonly the graft is made from the middle third of the patellar tendon of the involved knee. Grafts can also be created from hamstring tendons or harvested from cadaver tissue. Often, after surgery, patients demonstrate very limited motion, mobility, strength, and function. Crutches, modalities to control swelling, and often prescription anti-inflammatory pain medications are common initial measures after ACL reconstruction. Early physical therapy interventions are also utilized to facilitate early progress. Physical therapy can take several months. Increased risk of second ACL injury to either involved or uninvolved side is noted in those who do not complete formal rehabilitation.
While some people will try to rush recovery and finish rehabilitation at 6 months, it can leave the patient at increased risk of a second injury as they return to sports. Current evidence suggests 9 12 months is a more appropriate time frame for return to sports. This can be even longer if the patient does not participate in a proper course of rehabilitation. Return-to-sport testing protocols have been shown to be the best indicator of return-to-sport capabilities.
Due to ACL tears being non-contact in nature, prevention programs have been developed to minimize the risk of ACL tears. Identification of poor neuromuscular control and movement patterns is a good way to try to assess for risk of injury. Extra attention should also be payed to female athletes, athletes who participate in cutting sports, and individuals with previous ACL injury. Strength, balance, and movement performance testing can all provide information to help identify the risk an athlete may carry for serious knee injury. Once risk has been identified, a customized program focusing on balanced lower extremity strength, core strength, balance, and neuromuscular control with sports activities can be developed. This program should be carried out regularly to ensure best results with regards to prevention.