NEW YORK (Reuters Health) - A simple video analysis could spot which female athletes are at greatest risk of knee injury and therefore might benefit from preseason training.

On the basis of 49 high school varsity students assessed so far, video analysis appears to be a good screening tool for injury-promoting knee displacement, reported Dr. Timothy E. Hewett at the American Orthopaedic Society for Sports Medicine meeting in Sun Valley, Idaho.

Once the problem is detected, training programs may be able to reduce the occurrence of a particular knee injury suffered by female athletes--known as anterior cruciate ligament injuries--by as much as 80%.

Female athletes are five times as likely as men to tear their anterior cruciate ligament (ACL), a band of connective tissue that runs diagonally behind the knee and connects the shinbone to the thighbone, Hewett told Reuters Health. Considering the growing number of female athletes at the college level in the US, these injuries represent a serious problem.

"If you tear your ACL, you've basically bought yourself a car with the costs," Hewett said. With rehabilitation and surgery, expenses can easily escalate to more than $20,000, which adds up to $100 million each year across all US high school and college athletes, he said. On top of this are what the researcher calls "hugely traumatic effects" on athletes, who may miss class and whose grades may suffer.

In the early 1990s, researchers showed that female athletes are at greater risk for knee damage if their knees tend to turn in together when they land from a jump--a phenomenon known as "valgus" movement.

Hewett's group, from the Cincinnati Sportsmedicine Research and Education Foundation, showed that a 6-week training program could reduce these valgus movements in female athletes.

Before training, women's knees on average moved 5 centimeters (cm) inwards per knee when jumping from a foot-high box, whereas men's knees moved only 3 cm per knee. After a 6-week program that included single-leg balances, jumps and stretching, the women's knees moved only as much as men's.

"What we think is that this type of training can...prevent as much as 80% of ACL and other knee injuries in female athletes," Hewett told Reuters Health. The training program--90 minutes a day, 3 days a week for 6 weeks--used basic equipment that most colleges would have, he added.

The next step was to see if "we could identify which of these kids were at risk so that we could say 'outside a certain range of (knee) movement, you need to be trained."'

The researchers aimed a camcorder at the knees of athletes as they landed after jumping off a foot-high box. By placing a yardstick within the shot, they could measure how far the athletes' knees moved.

Considering that more than 1 in 10 of the 100,000 female athletes in the National Collegiate Athletic Association blow out their knees each year, Hewett said, the time taken to assess and train female athletes "is an investment worth making."

Details of the training program developed by Hewett and associates can be accessed at www.sportsmetrics.net.