The ACL (anterior cruciate ligament) helps stabilize and support the joint. A diagnosis of ACL injury describes a specific knee injury in which the ACL is partially or completely torn.
The knee is the largest joint in the body, and one of the most easily injured. The ACL is part of a complicated network of tendons and ligaments that help support the knee by stabilizing the femur (thigh bone), on the tibia (shin bone) and preventing the tibia from sliding and twisting during activity.
These structures are particularly vulnerable to injury during athletic activity or as the result of impact. “ACL tears are quite common,” according to Robert G. Marx, M.D., an orthopaedic surgeon at Hospital for Special Surgery (HSS) in New York. Tears of the anterior cruciate ligament are quite common, with between 100,000 to 200,000 reported each year in the United States.
“ACL injuries, partial or complete, usually happen during athletic activity as a result of sudden stops, changes in direction when running, pivoting or landing after a jump. If an ACL is not intact, the knee can become unstable, particularly during sport.” Although people of all ages and physical abilities and conditioning can tear their ACLs, the risk is much higher in females, and young girls are more susceptible than males.
Most ACL injuries are attributed to general core and lower body weakness. Athletes participating in skiing and basketball and athletes wearing cleated shoes, such as football and soccer players, are susceptible to ACL injuries. Those playing lacrosse and field hockey are also at high risk.
When the tear to the ACL is the only injury present, non-surgical treatment may be a viable option depending on the patient. A regime of rest, physical therapy and activity modification can be prescribed. A brace may be fitted for use during activities that would place special stress on the knee. However, the long-term outcome for patients who are treated non-surgically varies. Those who return to aggressive cutting and pivoting activities are likely to experience instability.
Because the ACL cannot be reattached once it is torn, surgical reconstruction requires the grafting of replacement tissue in its place. Multiple sources are used including the patient’s own hamstring tendons, patellar tendon, the quadriceps tendon, or an allograft (human donor tissue).
ACL reconstruction is performed using arthroscopic techniques, in which a combination of fiber optics, small incisions, and small instruments are used.
Reconstructive surgery is generally scheduled between three and six-weeks after the injury occurs in order to allow inflammation in the area to subside. If surgery is performed too early, patients may develop arthrofibrosis, a profound scar response. Orthopaedic surgeons gauge the appropriate timing of surgery based on the presence of other injuries (which may require more prompt attention), physical appearance of the knee, and the patient’s level of pain, degree of range of motion, and the quality of muscle control.
Following surgery, the patient enters a rehabilitation program to restore strength, stability, and range of motion to the knee. “Recovery time varies, with a period from about 6 to 12 months on average,” said Dr. Marx. Assessment of recovery is based on restoration of muscle strength, range of motion, and proprioception or joint position sense. The degree of pain associated with ACL recovery also varies and can be addressed successfully with medication.
“Research has clearly shown that some ACL injuries can be prevented with an appropriately designed program," Dr. Marx noted. Some facets of such a program are listed below: