Women and Anterior Cruciate Ligament (ACL) Injuries

Topic Overview

Women have more anterior cruciate ligament (ACL) injuries than men: women athletes injure their ACLs up to 8 times as often as men athletes.^{footnote 1} Experts have identified three areas where differences between men and women may affect the risk of ACL injuries.

• Body differences. Compared to men, women have a wider pelvis, a smaller ACL, a narrower area containing the ACL (femoral notch), and a greater degree of the knees pointing inward (genu valgum or knock-knee). These differences increase the risk of an ACL injury, especially when landing from a jump.
• Muscular differences. Compared to men, women have less muscular strength, use the muscles in the front of the thighs (quadriceps) more for stability, and take a longer time to develop muscular force at a given moment. These factors result in greater stress being placed on the ACL.
• Laxity and range of motion. Compared to men, women have a greater range of motion and "looser" knees (knee laxity), hip rotation, and knee hyperextension (how far the knee can be stretched or straightened). The increased hyperextension results in a backward curve of the knee when the leg is straight. This makes it more difficult for the muscles in the back of the thigh (hamstrings) to protect the ACL. Looser knees may also make an ACL injury more likely.

Some studies suggest that the differences in ligament laxity may be due to changing hormone levels. These studies have shown that there is change in ligament laxity during the menstrual cycle and that women are at greater risk for an ACL injury during the ovulatory phase of their cycle than at other times. Other studies have not found a relationship between the menstrual cycle and laxity in the ACL.^{footnote 2} How hormones affect the ACL is not known.

Training and rehabilitation

Training and rehabilitation programs for women may take the above factors into account. A program may include exercises to:

• Control inward movement of the knee.
• Emphasize using the hamstrings to stabilize the knee.
• Emphasize speed and reaction time of the quadriceps.
• Control hip and trunk movement and train the hip muscles to help stabilize the knee.
• Control knee extension.
• Increase muscular endurance.