It happens in a split second, the result of a direct blow to a planted foot, a sharp directional change to juke a defender, a sudden stop, or an awkward landing that hyperextends the knee. Although the “how” varies, most athletes are universal in describing what happens when they injure their anterior cruciate ligament, or ACL.

They hear a distinctive pop in the knee, which is followed by significant pain and swelling, usually within 20 to 30 minutes. The feeling of knee instability is usually a few days later.

Most ACL injuries are complete or near-complete tears. They occur most frequently in high-demand sports like football, basketball and soccer. The American Academy of Pediatrics reports the highest number of ACL injuries among high school athletes playing girls’ soccer, followed by boys’ football, girls’ basketball, girls’ gymnastics and boys’ and girls’ lacrosse.

Understanding the ACL and Injury Prevention

The ACL is one of the four main ligaments in the knee. Located in the middle of the knee, the ACL connects the thighbone and shinbone, providing knee stability and harmonious movement of the adjoining bones during twists and pivots.

Learning proper techniques for cutting, changing direction and landing can decrease ACL injuries. Most physicians support neuromuscular training to strengthen quads and hamstrings, as well as training to improve flexibility and balance.

Memorial Hermann | Rockets Sports Medicine Institute also focuses on core stability and hip strengthening. The latter is particularly important for teens and females.

Hip strength is super important in rehabilitation after ACL reconstruction surgery and in decreasing the chance of ACL injuries because it helps prevent the knees from rotating inward when landing, running or squatting. This inward rotation is referred to as knee valgus. It predisposes athletes to knee pain and ACL tears.

Treating ACL Injuries

A torn ACL will not heal without reconstructive surgery. Add to this a six- to 12-month rehabilitation period and ACL injuries can feel daunting to the best of athletes.

In general, a young healthy athlete should undergo ACL reconstruction. Not fixing it will lead to imbalance in the knee and a greater chance of arthritis in the future. Most ACL reconstructive surgery is conducted arthroscopically using a graft from the patient’s patellar tendon or hamstring tendon, or an allograft from a cadaver. During the surgery, doctors also look for and repair other knee injuries such as meniscus tears and chondral injuries.

The American Academy of Orthopedics estimates half of all ACL injuries occur in combination with damage to the meniscus.

Bringing the Knee Back to Health

It takes about six weeks for the bones that hold the new ACL to heal, but much longer for surrounding muscles.

Surgical ACL reconstruction is just one part of the process. The physical therapy makes or breaks the surgery and impacts the final outcome.

The first step in rehabilitation is getting the quad to remember how to fire and improving range of motion. This sets the framework for getting patients back to their sport.

Some physical therapists require patients to have strong enough quad muscle control to perform single leg squats before they can jog. Later, patients work on plyometrics, or jumping exercises, to promote proper jumping and landing techniques.

Overall, physical therapists stress patience during the long rehabilitation. Patients need to understand their injury and the healing timeframe so the knee can heal properly.

Learn more about ACL Injuries »

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