Estrogen's role

Estrogen appears to affect a female athlete's ligaments by making them more relaxed and boosting the risk for injury. The anterior cruciate ligament (ACL) in the knee seems particularly in danger of being injured because of this. The risk is even higher at certain times during a teen girl's menstrual cycle.

Physical differences in teen girls also affect the ACL and the knee. There is less space in a teen girl's knee for the ACL. This puts more stress on the ligament, making it easier to tear. Teen girls have wider hips than teen boys. This difference in width puts more stress on the knees, particularly when landing from a jump. When a girl lands, she has more flex in her ankle and more foot roll out.

The highest-risk sports for ACL injury include:

• Basketball

• Soccer

• Cheerleading

• Field hockey

• Singles tennis

• Lacrosse

• Ultimate Frisbee

• Skiing

In addition to knee injuries, teen girls may be more likely to have problems with shoulder instability and ankle sprains because of their more relaxed ligaments.

Reducing ligament injuries

Here are several suggestions for teen athletes:

• Strengthen leg muscles, particularly the hamstrings.

• Learn how to land correctly after jumping, with knees bent and hips flexed forward.

• Strengthen core muscles in the trunk, hips, pelvis, abdomen, and back.

• Warm up before beginning any activity, take rest breaks, and cool down and stretch after play.

Breast problems

Teen girl athletes may also have breast pain and discomfort because of friction, lengthy periods of motion, and depending on the sport, injury from a blow to the breast.

One of the best ways to prevent breast injury caused by motion and friction is to wear a well-fitting sports bra. The sports bra should limit breast motion as much as possible and be made of breathable material.

For teen girls who run or participate in other sports with repetitive running, the nipples may become irritated. Cold wind can make it worse. A well-fitting sports bra can reduce nipple injury. Petroleum jelly or bandages may also help.