The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments in the knee, and especially common in women. A torn ACL will make a knee unstable, making it difficult to play sports. Athletes who have suffered an ACL injury are at increased risk of developing arthritis later on in life, even if they have surgery for the injury. ACL injuries often take athletes out of competition for 6 months to a year.

Why do ACL injuries occur?

ACL injuries typically occur during deceleration and landing events. Both anatomic and external forces contribute to an ACL injury. Anatomic factors include hyperflexibility, knocked knee position, flat feet (pronation) and variation in hip muscle control. External factors include uneven ground and the playing surface itself, contact with another player and athletic shoes. Women tend to have more flexible knees than men and hip muscle coordination during landing and change of direction events may adapt at a slower rate than in men.

How do ACL injuries occur?

ACL injuries often occur as a noncontact event in close to 70% of cases. As previously stated, change of direction and landing is usually involved with the knee being almost straight at the time of injury

Prevention of ACL Injury

It is possible to significantly decrease the incidence of non-contact ACL injuries through sports specific training programs. The main focus of the program is on proper hip and knee muscle control and proprioception. Exercises focusing on strength, balance and stability are performed during activities of jumping, landing and changing direction. When landing, athletes are instructed to land on the balls of their feet and knees flexed with the chest inline with the knees and feet. Another focus is core strengthening exercises. The abdominal core is most important in body control and stability during exercise and sports. Activities combing core strength and balance can be done with the aid of an exercise ball and wobble board. To improve singleleg core strength and stability, athletes perform exercises such as jumping and landing on one leg with the knee flexed and then momentarily holding that position.

Plyometric Exercises

Plyometrics are a type of exercise used to increase the speed and force of muscular contraction. The training involves fast powerful movements which first lengthens a muscle (eccentric phase) then shortens it (concentric phase). This provides significant muscular power with the muscle unit in a lengthened position similar to that seen during sports. Typical activities include rapid sequence of jumping and landing focusing on proper hip and knee position. High-intensity plyometrics may be key in reducing the number of ACL injuries. Many of these exercises can be easily incorporated into a sports warm-up program. Coach and parent education is essential.