NEEDY KNEES

One of the most common and dreaded sports injuries among both professional and weekend athletes is tearing of the anterior cruciate ligament (ACL) that runs behind the knee to prevent the shinbone from moving too far forward (versus the posterior cruciate ligament, or PCL, that prevents the shinbone from moving too far backward). ACL injury is serious and can sideline an active person for extended periods of time -- and frequently requires surgery to repair.

Special problem: The rate of ACL injury among women is disproportionately high. Based on per player hours, it is twice as high among female basketball players as male -- and among female soccer players, it is a whopping four times as high. Although statistics are not available for tennis players, ACL injury is a major sideliner there, too. With stats this significant, researchers have made special efforts to understand why women are at extra risk and how they might minimize it.

RESEARCH FINDINGS

Research thus far has looked at such factors as hormone fluctuation due to the menstrual cycle, and underdeveloped hamstring muscles as possible causes for women's vulnerability. Now a study has emerged from a team at the University of North Carolina-Chapel Hill that researched how women's posture as they perform maneuvers creates stress on the ACL. Working with a group of elite soccer players, the researchers found that women tend to keep their trunk and hips in a more erect posture while running and jumping, whereas men employ more flexion in their trunk and their knees during these same actions. This difference, the study concludes, likely contributes significantly to the ACL problem in women.

ANALYZING THE FINDINGS

I spoke with orthopedic surgeon Beth Shubin Stein, MD, of the Women's Sports Medicine Center at the Hospital for Special Surgery in New York City about this study's conclusion concerning women's ACL problem. She agrees with it and adds that it is the latest of several studies to produce overwhelming evidence that ACL injury has to do with the way women land after a jumping or taking-off position and how they turn on a dime, as she put it. Women perform these maneuvers with a much straighter leg than men do, she says, thereby putting great stress on the ACL. Adding to the problem, women's muscle structure is dominated more by the quadriceps (on the front of the thigh) than men's, because they have more strength in the hamstring muscles in the back of the thighs, which provides more stability to the knee.

Women don't have sufficient knee flexion in part because of their anatomy, says Dr. Shubin Stein. On the one hand, women's proportionately wider hips often create a sort of knock-knee (technically called genu valgum) stance, which places pressure on the ACL. On the other hand, for a woman who is not knock-kneed, unless she has strongly developed muscles in her buttocks, quads and hamstrings, her knees will automatically turn in when she is landing a jump or performing the other motions pertinent to ACL injury.

REVERSING THE PATTERN

The answer? Retrain women to hold themselves and bend their legs the way men do to better protect their ACLs. According to physical therapist Theresa Chiaia, also of the Women's Sports Medicine Center, there is a real need for coaches to become more aware of the importance of revised training protocol.
The first aspect of this is something called proprioception training, which is the feedback mechanism in the body that sends the brain information that allows it to keep track of joint movements. Through proprioception training, women become more aware of their body movements and learn if they are holding and moving themselves properly -- proprioception is the messenger that tells you where you are in space. Proprioception training starts with simple maneuvers, such as standing on one foot, and escalates to dynamic activities, such as jumping and hopping.

Chiaia says that as part of a good training program, women also need to strengthen the muscles supporting the knee -- the buttocks, quads, hamstrings and ankle muscles -- as well as increase their flexibility and range of motion. Any woman who participates in start-and-stop sports such as tennis, racquetball, skiing or even certain types of dance should retrain her body for better ACL protection.

HORMONAL CONNECTION

Daily Health News contributing editor Andrew L. Rubman, ND, points out a key vulnerability in women who have not yet reached menopause -- the same hormonal shifts that allow an egg to break free of the ovary during ovulation also allow tendons, ligaments and cartilage to be injured far more easily. I will follow up on this point and its implications in a future article, but thought it important to mention here.
As for strengthening your muscles, Dr. Shubin Stein strongly recommends working with a physical therapist who can develop a set of exercises for you. Chiaia says that depending on a woman's starting level, a six-week course is generally sufficient. But as with all types of exercise, regular practice of your training program is necessary.