Active women are at least twice as likely to suffer serious knee injuries as men, but it’s not just athletes who are at risk.

Although female athletes at the high school and college level suffer serious knee injuries, women who play recreational volleyball or participate in step aerobics also can injure their knees, says the American Academy of Orthopaedic Surgeons (AAOS). A mother who carries her child down a flight of steps and misses the last step also can injure her knee. In short, a knee injury can happen to any woman, no matter how athletic she is.

The chief movements that cause knee problems in women are pivoting and landing from a jump, the AAOS says.

Luckily, women can help protect themselves by getting into better shape, knowing their strength, controlling their weight, and exercising their leg muscles.

Anatomy of the problem

Why are women’s knees, in a sense, their Achilles heel?

Since a woman has a wider pelvis, her femur (thigh bone) descends into the knee at an inward angle.

When a woman becomes fatigued, as during an athletic event, the angle on landing becomes more pronounced, further increasing the chance of injury.

A band of fibrous connective tissue called the anterior cruciate ligament (ACL) passes through a “notch” in the lower end of the thighbone that forms part of the knee. The ligament, one of several that attach the upper and lower leg bones, is about the same size for a woman as a man — but the notch is up to 20% narrower in women. That makes the woman’s ligament more susceptible to tearing.

A woman’s hamstring muscles, at the back of the thigh, are often weak compared with her quadriceps, the muscles at the front of the thigh. The quadriceps pull the bones of the lower leg forward, and the hamstrings pull them back. Hamstring muscles help protect the ACL from injury. When the pulling power is out of balance to the rear, the knees suffer.

The muscle imbalance is far worse in women than in men. The imbalance may begin to happen during childhood if girls engage in less physical activity. Exercise can help overcome the problem.

Risk of injury to the ACL appears to be higher during ovulation, when estrogen levels are highest. The ACL appears to respond to estrogen by decreasing cell activity to repair basic ligament fibers called collagen.

Strengthen your legs

Strengthening exercises are especially important for your hamstrings. Try hamstring curls: Lying on your abdomen, draw your lower legs upward, and try to touch your heel to your buttock. Use resistance equal to about 10% of your body weight. Do a few sets of 10 to 15 repetitions; hold them a second or 2.

Jumping exercises are also critical for building strength and preventing knee injuries. When you land from a jump, keep it soft. Come down on the balls of your feet and slowly roll back to the heel. Keep your knees bent and your hips straight. Try to keep your knee in line with your foot.

Hopping over a cone side to side and forward and backward builds strength and control:

• Place a 6-inch cone on your left. Hop over the cone with both feet, concentrating on a soft landing. Repeat by hopping back over the cone to the right. Repeat for a total of 20 hops.
• Place the cone in front of you. Hop over the cone with both feet, then hop backward over the cone. Keep your knees slightly bent when you land. Repeat for a total of 20 hops.
• Repeat the above forward and backward exercise, but hop with 1 leg at a time. Again, keep your knee slightly bent when you land. Do 20 hops on each leg.

Other knee tips

• Improve your overall strength and fitness.
• Know your level of fitness and the demands of your sport or activity.
• Control your weight. When you walk, each extra pound adds 4 pounds of pressure to the kneecap. Climbing steps, that pound adds 20 pounds of pressure.
• Buy sturdy shoes made for your activity, and replace them when the inner or outer soles appear worn.