In his 22 years of coaching soccer, Frank Baumholtz had never seen anything like what he saw last fall.

One by one, players on his Pearl City High School girls team suffered the most devastating of athletic injuries: An ACL tear.

The knee injury sidelined six girls.

"It was a nightmare," Baumholtz said. "Every time you played a game, you wondered who was going to get hurt."

His injured players were strong, experienced athletes in the prime of their high school careers. Baumholtz saw no obvious pattern in the events. There were collisions with other players that produced ACL tears and tears that happened two strides away from the nearest opponent, which was the case in a scrimmage against Castle High School.

When the Castle player turned, his player responded — and just that fast, her season was over.

"Our girl stopped, pivoted and kind of flipped through the air and landed on her back screaming," Baumholtz said. "She didn't hit anybody, nothing. She just tore it out."

But a torn anterior cruciate ligament has become more common among female athletes, especially in soccer, basketball and volleyball. One local physical therapist calls it an epidemic.

According to a study published in the Journal of Athletic Training, female high school athletes have a one in 100 chance of suffering a tear. That number rises dramatically in college, however, to one in 10. ACL tears are believed to be six to nine times more likely among teenage girls than their male counterparts.

"I think it is very, very serious," said Michele Nagamine, who coaches girls youth teams at Leahi Soccer Club, varsity girls at Kamehameha Schools and the women's team at Hawai'i Pacific University. "We have had an obscene number of injuries in the last year. It has been very discouraging."

Eleven of Nagamine's Leahi players have suffered ACL tears in the past 18 months, including two girls who tore the ligament twice. The number of injuries prompted Leahi to begin testing prevention programs this spring with players as young as 11.

The ACL is critical to the stability of the knee joint. The finger-sized ligament connects the femur to the tibia. Female athletes are more prone to these tears, in part because their ligaments tend to be looser and their hips are wider. Both factors can lead to leg instability when landing from a jump.

Reconstructive surgery is complicated and the recovery, which can be painful, can last as long as a year.

Jaco Van Delden, a Honolulu physical therapist whose practice averages two new ACL injuries a week, started working last September on a program to evaluate the risk of injury. He wanted objective tests and teamed up with Joe Smith, an athletic trainer at the University of California-San Francisco, to develop video analysis and specific measurements to gauge weaknesses.

They created four tests to measure abdominal strength, aerobic fitness, ability to balance on one leg and the ability to jump and land correctly.

Although no single test outweighed the other, Van Delden said, knee alignment is important, whether running, turning or landing.

"A lot of girls, when they land from a jump, there is no proper shock absorption in the body and especially the knees and the hips," he said. "When they land, their knees cave inward."

Smith said little research has been done on the problem of ACL injuries among female athletes, but known risk factors include anatomical makeup, higher levels of estrogen, playing surfaces and the only factor a trainer can hope to change: "neuro-muscular patterns."

"It's specifically contributing to movement patterns of the individual," he said. "How a person lands, how soft they land, if they land on the balls of their feet vs. their heels."

In March, the pair tested their program on 70 girls from the Honolulu Bulls Soccer Club. To gauge their jump mechanics, Van Delden and Smith taped markers on a player's kneecaps and hips and had the player jump down from a 12-inch-tall box. They videotaped the motion and replayed it for the athlete.

Nearly 90 percent of the girls failed to land in a way that would protect their knees. And most of them were unaware of what was happening.

"I think it was an eye-opener for them," said Michael Guidry, the Bulls' assistant director of coaching.

The players were told what exercises they could do to help correct their problems and the Bulls also began a club-wide training program to help reduce injuries.

"It is very logical and makes sense," said Derick Kato, director of operations for the Bulls. "They were actually measuring something. You are measuring different disciplines, scaling and scoring the players."

Kato says it will take three to five years of observation to know how well the program works. Van Delden and Smith plan a second round of evaluations in September, when they also plan to re-evaluate their first test group.

The broader community of coaches need to learn more about ACL injury prevention, said Kato, who has contacted other soccer clubs to explain the importance of adopting a program.

"These are kids, and their health and safety are important," he said.

But Kato said he is already seeing a change. During a recent game, one of his girls collided with an opponent but landed correctly. The opponent had to be helped off the field.

"Subconsciously or consciously, athletes are going to be making the connections," Kato said. "Does the program work? Absolutely. That's proof right there."