Women are four to six times as likely to suffer from an ACL injury as men. This is thought to be due to several factors. A wider pelvis makes for a sharper angle where the femur (thigh bone) meets the knee in women. Estrogen receptors on the ACL may cause the ligament to become more lax (and therefore more injury-prone) during menstruation.
Perhaps most importantly, women simply don't achieve the same neuromuscular spurt in puberty as do men; this is seen by many researchers as a key to the body's adaptation to the growth and development that occurs then -- and of particular importance for athletes.
This neuromuscular change is defined as an increase in power, strength and coordination to accompany an increase in height and weight. Without such increases, the joints bear more of the stress from ground reaction forces, and the muscles bear less. Notably, there is no documented difference in rates of ACL injury between genders in prepubescence.
Steps for prevention
Women can take several steps to help prevent ACL injuries. The sudden pivoting that often precipitates these injuries, as well as abrupt accelerations followed by sharp decreases in speed, require a learned awareness of knee position during activity. In absence of a personal trainer who can administer verbal cues to keep you on track, learn to think of your knee as a hinge, not a ball and socket.
If you play recreational tennis, basketball or volleyball, train yourself to default to the flexed knee stance known as the "athletic position": feet under shoulders, knees over toes, weight distributed evenly under you.
Learn to achieve this position not only prior to a volley, but before cutting movements as well. Make yourself decelerate before cutting, and focus on "soft landing" (toe-to-heel rocking with bent knees). Balance board exercises may also increase knee position awareness, though studies reveal mixed results.
Sport-specific exercises that not only strengthen the knee joint and surrounding muscles but teach safe landing techniques have proven of use in preventing ACL injuries. Proper technique is essential -- avoid these exercises when you are fatigued, and always adhere to a policy of gradual build-up.
To perform squat jumps, go from the athletic position down to a squat, and then jump vertically until your legs are nearly straight; land and end in the athletic position.
In the hop-and-hold, jump forward just a few inches and land on a single leg with deep knee flexion. If you are recovering from an ACL injury, only attempt this after initial rehab, and gradually increase the jump distance over time. Those in the earliest phase of training, too, should start with simpler exercises.Hamstring strengthening in the weight room can do much to attenuate injury risk. Research has repeatedly shown that women tend to favor their quadriceps while running, jumping and cutting. Men rely more on their hamstrings. When you favor your quadriceps muscles in sports maneuvers, you tend to increase movements that extend the knee rather than flex it. This puts undue strain on the ACL, whose job is to prevent over-extension. By strengthening the hamstrings, you'll counteract this tendency to land with a straighter knee.
(J. Athl. Train, 2004, Vol. 39, No. 4, pp. 352-364)
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