The University Record, June 25, 1996

Poor training, anatomy are blamed for knee problems of many female athletes, U-M researchers say

U-M researchers have found that women who play soccer, basketball and volleyball suffer twice as many knee injuries as their male counterparts.

Photo by Bob Kalmbach

By Michelle Donaldson
Medical Center Public Relations

"Women athletes beware," says Laurie Huston, research engineer in the Orthopedic Surgery Section and co-author of the study. "They are much more likely than male athletes to experience a rupture or tear of their anterior cruciate ligament (ACL). This is one of the most common knee injuries, but also one of the most devastating."

According to a study conducted at the U-M Health System, female athletes experience knee injuries at twice the rate of their male counterparts, especially when it comes to such sports as soccer, basketball and volleyball---those that require constant pivoting. The cause of this gender gap, the researchers say, is a combination of anatomy and poor training. The result: a type of injury so serious that it requires surgery to repair and can sideline amateur and professional athletes alike for up to a year.

What clinicians call "rupturing the ACL," but what is more colloquially known as "blowing out" one's knee, involves the tearing of the ligament that runs behind the kneecap. This ligament ropes the thighbone to the shinbone and holds the kneecap in place. Once this "rope" is torn, the knee tends to slip and slide. While the condition usually can be repaired with one operation, rehabilitation can take six months to a year.

Huston and co-author Edward Wojtys, associate professor of surgery, believe that this susceptibility is due in part to physiologic characteristics in women such as wider hips, which place greater pressure on the inside of the knee; looser joints, perhaps due to the presence of the hormone relaxin; and lower levels of leg-muscle strength and endurance. But probably the most crucial difference between the sexes is in the "recruitment order" of knee muscles---the order in which the muscles around the knee tighten in rapid-fire succession to hold the knee snugly in place.

"The muscles around the knee are critical to keeping it in place," Huston says. "The faster these muscles tighten, the more protective they are."

Ideally, this process is a sort of dance of the hamstrings (the muscles behind the knee) and the quadriceps (those in front). The hamstrings should lead the response, tightening first. But often in female athletes the opposite occurs: the quadriceps tighten before the hamstrings, thereby weakening the knee.

The reason for this, they believe, primarily has to do with training. Women often spend more time doing bench presses and leg extensions, which strengthen the quadriceps, and pay little attention to working the hamstrings.

"Female athletes tend to work on their quadriceps more because they strengthen quickly. They think their legs are getting stronger, but they are really not. They need to do activities that increase the quickness of the hamstring response, in addition to exercises that build up the quadriceps," Huston says, referring to activities such as hamstring curls and jumping rope.

Based on her study, Huston believes this "mistraining" is happening at all levels, from high school to the Olympics. Currently she and Wojtys are proposing a study that will look at different training regimens for female athletes in an attempt to recommend one that increases the hamstring response time and thereby lowers the risk of knee "blow out."