ACL injuries often result in a “pop” in the knee, followed by a feeling like your knee is about to give out. These injuries are common, affecting roughly 1 in 3,500 people in the U.S. each year. This is particularly true for young female athletes, who experience ACL tears up to eight times more frequently than their male counterparts.
The increased risk is thought to be due to a number of factors, including anatomy, muscle strength and hormonal influences, says Elizabeth Matzkin, MD, Mass General Brigham Orthopaedic Surgeon and Sports Medicine specialist and Chief of Women’s Sports Medicine at Brigham & Women’s Hospital. Females may be more likely to rely on their quadricep muscles when slowing down, which could put extra stress on the ACL.
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An ACL injury is a sprain or tear of the anterior cruciate ligament, a strong band of tissue in the knee connecting the thigh bone to the shin bone. Athletes who participate in sports involving sudden stops or pivots — including soccer, basketball, field hockey and downhill skiing — are the most likely to be affected.
ACL sprains or tears typically occur suddenly when an athlete engages in a knee-straining motion while in play. Slowing down or stopping abruptly and switching direction, landing awkwardly from a jump, or pivoting with the foot planted firmly on the ground are common culprits. A direct blow to the knee can also injure the ACL.
While ACL tears may be managed with physical therapy/rehabilitation alone, they typically require surgery in order for athletes to return to competitive sports.
Surgery involves reconstructing the ACL, either from the patient's own tendons or the tendons of a deceased donor. In both cases, skilled surgical technique is crucial for a successful outcome, Dr. Matzkin says.
Females have had less successful outcomes after ACL reconstruction in the past compared to males. Female athletes may benefit from advanced surgical techniques and using a robust tendon graft.
"Rather than relying on a smaller tendon graft, we now have graft options and techniques to ensure a larger and stronger graft,” Dr. Matzkin says. "If we can give our female athletes an adequate graft diameter, we've shown that our outcomes in females and males are equivalent."
For the most successful outcome, patients should work closely with their surgeon to determine the best graft choice based on their sex, age, sport and future athletic pursuits.
"For every patient I see," Dr. Matzkin says, "we talk about graft choices, what their sport is, and what their goals are. That plays a role in deciding what the graft choice is. Working together, we can ensure patients are getting the individualized treatment they need to return to activities."
After surgery, there will be six to 12 months of individualized rehabilitation. This helps restore mobility and range of motion to the knee and strengthen the supporting quadriceps and hamstring muscles. In fact, a surgery's success is largely determined by a patient's dedication to physical therapy.
Being out of sports and activities for patients after injury and surgery can be difficult, but it takes time for the new ACL to heal and time to regain motion and strength. "One of the hardest things is the mental component of being out of sport for so long," Dr. Matzkin says.
It's important for recovering patients to keep their long-term goals in mind. Successful surgeries paired with rigorous rehabilitation is the best way for an athlete to regain full knee function, and appropriate rehabilitation results in a lower chance for reinjury.
Not every ACL injury can be prevented. However, regular preemptive neuromuscular training aimed at strengthening the thigh (quadriceps and hamstring), hip and core muscles can reduce an athlete's risk for injury.
"Athletes need to have proper strength, balance, landing form and techniques specific to their sport in order to reduce risk of injury,” says Dr. Matzkin.
The most effective exercises include:
In many cases, they can be performed as part of a warmup – both U.S. Club Soccer and the National Federation of High Schools offer free resources for coaches and trainers. Serious athletes with ambitions to play in college or professionally may benefit from working one-on-one with a professional, Dr. Matzkin says.