What is the ACL?

The ACL – anterior cruciate ligament – is probably the most important ligament in the knee. (A ligament connects one bone to another.) The ACL, which is located in the center of the knee, connects the thigh bone (femur) to the shin bone (tibia). The main function of the ACL is to stop forward movement of the shin bone on the thigh bone.

What causes ACL injuries?

Most ACL tears are non-contact injuries. You can tear your ACL when you twist your knee too forcefully, or when you plant your foot and then suddenly change direction.

What athletes are at an increased risk of ACL injuries?

ACL injuries seem to be increasingly common. In college football, the risk of tearing the ACL and needing to undergo reconstruction in a four-year career may be as high as 16 percent. High-risk sports are football, basketball, soccer and volleyball. Females are four times more likely to have an ACL tear than males are.

What does an ACL tear feel like? What are the symptoms?

Typically, the athlete will feel or hear a "pop" or a sense that the knee "gave out." The athlete is unable to continue due to pain and instability. The knee usually becomes swollen anywhere from two to six hours after the injury, and it will stay swollen for two to four weeks. When the swelling subsides, the instability is still present and will give the athlete a feeling of unsteadiness.

How is an ACL injury treated?

After a physical exam, an X-ray will be taken to rule out any fracture. An MRI (magnetic resonance imaging) scan will be taken to get a clear picture of the knee. The MRI will show the soft tissue (ligaments, cartilage and muscle) of the knee. The torn ACL will show up clearly on an MRI. If the athlete wants to continue in his/her sport, ACL reconstruction is necessary. Fifteen or 20 years ago, tearing the ACL meant an athlete’s career was over, but now it is just put on hold until ACL reconstruction surgery and rehabilitation have been completed.

What happens after ACL reconstruction?

The first week after surgery, the athlete will perform gentle range-of-motion exercises, isometrics for strength, and some weight-bearing exercise. As the time progresses, formal physical therapy is started, including advanced strengthening and balance activities.

After about eight to 12 weeks, sport-specific activities are added to the rehab program, such as hopping, jumping and agility drills. The athlete should be able to return to normal activity anywhere from six to nine months following the ACL reconstruction.

Are ACL injuries preventable?

No. ACL injuries are going to occur. However, training techniques have attempted to minimize the risk of tearing the ACL. These include fine motor control of the lower extremities as well as increasing strength, endurance and flexibility. Luckily, with advances in surgical techniques (like ACL reconstruction) and rehabilitation, an ACL knee injury is a season-ending injury – but NOT a career-ending one.

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