Amy Taylor felt the pop, crumpled to the floor and knew immediately that her college basketball season was over.

For high school junior Taryn Flagg, the awkward twist triggered a peculiar twinge in her knee. She tried to play field hockey through it, then basketball, only to discover that ibuprofen wouldn’t touch the pain and ice couldn’t contain the swelling.

Dr. Nancy Cummings, an orthopedic surgeon from Farmington, feels a kinship with every aching athlete whose crutches creak the floor in her office. Her compassion can’t save six precious months of their athletic career, though. And her steady hands are their only hope of getting back to the court, the grass or the hill.

Cummings notices another eerie common denominator. Those wounded knees almost always belong to young women.

Anyone who regularly reads the sports page knows NFL, NBA, NCAA … and ACL.

Those last, ominous letters stand for anterior cruciate ligament, the portion of the knee that provides stability and a proper range of motion.

About 80,000 athletes will suffer an injury this year to the ACL or a closely related ligament that requires a full reconstruction. Most will fall between the ages of 15 and 25.

According to widely accepted estimates, at least four out of five will be female.

“It’s an epidemic,” said Cummings, the director of orthopedic surgery at Franklin Orthopedics. “Sports Illustrated, maybe five years ago, had a cover story on a women’s basketball team. I think it might have been Iowa. All five starters in the photo had ACL reconstruction. And they’re coming into my office younger all the time.”

To take an informal survey, simply attend any girls’ basketball, soccer or field hockey game or cheerleading competition. You won’t even need to ask questions. Take inventory of bulky knee braces and awkward tape wrappings. Good luck finding a team that hasn’t been affected by at least one major knee surgery.

As Cummings acknowledged, some college benches are a glorified infirmary.

The number of games and the intensity of competition double. Women with no history of knee injuries often experience that telltale pop. Some who blew out one knee in high school arrive at an innocuous jump stop and feel the other one let go.

“We’ve seen many very, very good players go down with that injury,” said Jim Murphy, who has coached women’s basketball and soccer at Bates College in Lewiston for 11 years. “There was almost never contact involved. It never looked serious.”

But Taylor and teammate Katy Dutille knew the gravity before Murphy or a trainer scuttled across the floor to assess the damage. For both, it was the second time around.

“The first thing each of them said was, Nope. It’s over.’ And it’s true,” Murphy said. “I’ve seen some women come back from one ACL injury and I would swear they almost look quicker. But not after the second one.”

Many risk factors

Doctors, trainers and coaches don’t know for sure why women suffer four to eight times more catastrophic knee injuries than men. But there are commonly accepted risk factors and theories.

Anatomical differences may play a role. Women typically have a wider pelvis, which puts a higher level of stress on the femur (thigh bone) and knee during landing.

“Not that much of a difference,” said Bates trainer Nancy Fournier, “but just enough to cause more injuries.”

The ACL travels through a groove in the bone known as the intercondylar notch. Research shows that the notch tends to be smaller in women than men, causing a possible “guillotine” or shearing effect on a hard landing.

Studies also show that the strength gap between the hamstring and quadriceps muscles is higher in women.

“We’re all careful not to say that it’s because women aren’t as strong as men,” said Chris Sementelli of MaineGeneral Sports Medicine in Waterville, “but it is true that there is a different quadriceps-to-hamstring ratio.”

Sementelli has been a certified trainer to local high schools, including Winthrop and Oak Hill, for 15 years. He strongly urges schools to implement prevention programs that emphasize the importance of strengthening all the leg muscles.

Both Sementelli and Cummings say there are inherent differences in the way girls and boys land when they jump. Boys tend to land in a bent-over, athletic position, while girls typically demonstrate a straight or “knock-kneed” stance.

Youth sports coaches might be able to reverse that tendency by employing plyometric (jumping) techniques as a regular element of practices and team workouts.

“When you coach kids with repetition, you build muscle memory,” Sementelli said. “As a result of that, we have seen a drop in the number of girls sustaining injuries.”

Damage: Sudden, or gradual

Not enough of a drop, though.

When the Monmouth Academy girls’ basketball team made its first foray to the Class C regional quarterfinals in 20 years last month, one of its seniors, Bianca Cloutier, missed the game due an ACL tear she suffered late in the regular season.

Then there’s the case of Taryn Flagg, a junior at Livermore Falls High School.

She’s a multi-sport athlete, as explosive with a field hockey stick as she is with an open jump shot. Her basketball coach, Frank Donald, says she was a lock to score 1,000 career points.

Somewhere between Friday field hockey games and Sunday fall-league basketball contests, Flagg got hurt. She doesn’t remember precisely when or how it happened. She just knows the daily transition from turf to hardwood didn’t help.

Neither did the pain medication or the freezer packs.

“There were sacs of fluid on both sides of my knee. I could still walk and run on it,” Flagg said. “But I was worried, my parents were worried, and my coach was worried. Finally we all decided it was time to get an MRI. That’s when they found it.”

Flagg’s injury was a torn meniscus. That’s a type of cartilage found between the bone ends in the knee, the area that bears the weight of a sudden stop. It’s shaped like a half-moon.

An athlete may tear the meniscus during a twist or landing, and it’s common for the meniscus and ACL to be torn concurrently. Flagg was a victim of the same biological factors that have sidelined thousands of other girls.

“I was told that I very likely would have torn my ACL sooner or later,” Flagg said.

Flagg underwent surgery on Tuesday, Feb. 8. While the procedure wasn’t a reconstruction in the purest sense of the word, it was rife with complications.

Her surgeon discovered more extensive damage than the MRI conveyed, including additional tears and deterioration. The operation took some 90 minutes longer than was predicted.

Flagg still hopes to fulfill the initial prognosis: three months without sports.

“Even if it takes a month longer than they think, that gives her a month to prepare for summer basketball,” Donald said.

The coach is optimistic because his pupil is working with Cummings. Donald met the surgeon at a recreational basketball game in Farmington.

“She’s had hip surgery something like six times herself,” he said. “She’s an athlete, so she understands that competitive nature. She knows the kid wants to get back, and she’ll do anything she can to help her.”

Exercises might help

Three miles north on Route 4, Jay High School girls’ basketball coach Chris Bessey instructs his team in jumping and leg strengthening exercises.

Bessey’s interest in the subject matter spiked last summer, when he learned that his daughter, Jordann, a freshman, is predisposed to an ACL tear.

Jordann was making that same odd transition as Taryn Flagg: Field hockey on summer mornings, basketball in the afternoons. Then her knees developed that same unsettling ache.

“Her therapist has her doing exercises to strengthen her thigh muscles. She’s riding a stationary bike quite a lot,” Bessey said. “She plays three sports. That’s probably part of the reason for these serious knee problems. Those different surfaces caused a lot of strain.”

Most experts recommend cross-training as a healthy way to expose the knees to different stress levels. But it can negate the positive effect of those strength and conditioning exercises.

“What we teach for cheerleading,” noted Sementelli, “is different than what we teach for softball.”

Sementelli says his hospital experienced a “rash of ACL injuries” three or four years ago. He believes education has caused the numbers to drop a bit. Cummings hasn’t detected such an optimistic trend in her practice.

At Bates, Fournier says she didn’t treat any winter athlete for a major knee injury this year.

“Knock on wood,” she added.

The experts agree that the explosion of girls and women playing competitive sports is a good thing. They also acknowledge that it has something to do with the alarming numbers.

Thanks to required Maine Principals’ Association training, most high school coaches are aware of ACL risk factors. Trainers and surgeons know, however, that the day-to-day challenge of trying to win games puts preventive exercise on the back burner.

“ACL injuries seem to be cyclical,” Sementelli said. “But the difference (between women and men) is very real.”