Weak in the Knees?
Hormones and anatomy make women more prone to knee injuries.
Anatomy, Hormones, and Technique
Why are women so prone to knee trouble? 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. But with bent knees, the force drops by 25%.
"It's like pulling an extra person off your back," he says.
Female athletes also tend to develop strong quadriceps muscles and relatively weak hamstrings -- a dangerous imbalance of power, Hewett says. The quads tighten the ACL, while the hamstring muscles relax it. Men generally flex their hamstrings whenever they strain a knee, protecting the ACL. Women, on the other hand, have a tendency to contract their quads.
Nobody knows the cause of these bad habits. "It could be genetic, or it may have something to do with training," Hewett says. Whatever the source of the trouble, it starts early. Hewett has noted straight-legged landings and weak hamstrings in girls as young as eight years old.
Prevention Through Training
With these dangers in mind, Hewett and colleagues developed a six-week training program that incorporates stretching, weight lifting, and seemingly endless jumps with flexed knees. "It's all about mimicking situations that can cause injuries, but staying in control," he says.
In addition to teaching proper jumping technique, the program works to strengthen hamstrings and improve overall balance and agility, says Hewett. Any activity that increases balance and control can help ward off knee injuries, he adds.
The results have been impressive: As reported in the November/December 1999 issue of the American Journal of Sports Medicine, 366 female high school athletes who completed the program were about four times less likely than comparable athletes to suffer a knee injury during a season of play.