And practically every team they face includes at least one player in a knee brace. Soccer, volleyball, softball, and other activities that involve jumping, sudden stops and starts, and rapid pivots can all rip a woman's knee ligaments with remarkable ease, he says. And while nobody knows how often casual athletes injure their knees, it's not a rare event, says Hewett, citing a recent study of recreational soccer players that found that women were roughly five times more likely than men to seriously damage their knee ligaments. Such statistics can be frightening, but with proper training and conditioning, Hewett says, almost any woman can lessen her chances of a knee injury. And with the first-ever scientifically proven program for preventing knee injuries in female athletes, developed by Hewett and his colleagues, safe play may be more possible than ever.
Biology is partly to blame.
A woman's relatively wide hips put extra stress on her joints, and female hormones seem to weaken ligaments, Hewett says. A woman can't do much about her anatomy or hormones, but other factors are within her control. First of all, women can learn to bend their knees when landing from a jump. Many female athletes invite trouble by keeping their legs straight when they jump, pivot, or land, which requires the knee to absorb a shock equal to four times a woman's body weight. The quads tighten the ACL, while the hamstring muscles relax it.