NEW YORK — Sheryl Swoopes heard a "POP" and let out an ear-piercing scream as she collapsed during a routine layup.
Rebecca Lobo landed on the floor of Madison Square Garden after going for a rebound, grimacing and clutching her knee under the basket as her teammates ran upcourt.
Two marquee players sidelined by the all-too-common anterior cruciate ligament tear. Nearly one in five WNBA players have had ligament tears, which league president Val Ackerman calls "one of the more important issues confronting women's basketball today."
Swoopes' April injury, which included a lateral meniscal tear, will require at least six more months of rehab before she can rejoin the four-time champion Houston Comets.
Lobo is back with the New York Liberty, but she missed two seasons with yet another ACL tear six months after the first.
"I wouldn't wish it on anybody," Lobo said.
NCAA data shows female athletes are four times as likely to tear an ACL as male athletes who play basketball. Susan Craig Scott, team physician of the Liberty, refers to the "epidemic" of knee injuries.
There are no definitive answers why women are more susceptible. But studies suggest the reasons include the differences in the strength of quadriceps and hamstring muscles and the size of the notch where the ligament attaches to the femur.
Women, in general, also have wider hips than men, and that increases the angle of the knee when landing, another possible factor.
"The latest thinking is it's a kind of muscle imbalance" where the hamstrings are not as strong as the quadriceps muscles, Scott said.
"Conditioning needs to be focused there as a preventative measure. The knees have to be bent prior to impact to act as shock absorbers."
Thirty-five of the 203 players in the WNBA (17.2 percent) have had a ligament tear at some point in their basketball careers, spanning college, pro leagues overseas, the WNBA or now-defunct ABL.
Nine players are currently sidelined with knee ligament injuries in the 16-team WNBA.
"Almost everybody you meet has a scar on their knee," said Comets guard Coquese Washington. "They've either had a torn ACL, meniscus or arthroscope."
Season-ending injuries to high-profile athletes are raising the level of concern. Swoopes' layup during a preseason pickup game ended the WNBA's marketing dreams involving the heir apparent to retired superstar Cynthia Cooper.
Swoopes was coming off an MVP season, shooting 51 percent, leading the league in scoring and earning defensive player of the year honors.
"The good news is that ACL injuries in women do seem to be treatable and most, if not all, players can now come back from them," Ackerman said.
Five of 11 players on the gold-medal 2000 U.S. Olympic team — Ruthie Bolton-Holifield (Sacramento), Yolanda Griffith (Sacramento), Natalie Williams (Utah), Katie Smith (Minnesota) and now Swoopes — have had ligament tears.
Minnesota coach Brian Agler has seen a number of knee injuries in his 18-year coaching career. At one point, six players on his ABL champion Columbus Quest team had suffered ACL tears.
"It's always a non-contact injury," Agler said. "They're either taking off or landing. For some reason, it's when the weight is really bearing down on that one knee.
"It definitely impacts our sport."
Swoopes, who began light shooting and agility drills last month, drove untouched to the basket at the Westside Tennis Club in Houston. She planted her left foot and the knee buckled.
"We knew it was serious by the way she was screaming," said Washington, who tore her ACL at Notre Dame. "I've never heard a scream like that before. It was extremely intense."
Two surgeons needed four hours to repair Swoopes' ACL and she had to avoid weight-bearing activity for a month.
Comets trainer Michelle Leget has to stop the 30-year-old Swoopes from doing too much in rehab.
"She's slightly ahead of schedule, considering the seriousness of the damage," Leget said. "She's done a ton of strengthening."
Daily four-hour workouts include swimming, weightlifting and bike riding.
"I am trying to get my range of motion back lifting weights," Swoopes said. "I think athletes tend to forget about their good leg during rehab, so I am working on my good leg as well."
Of three original marquee players, only Lisa Leslie of the Los Angeles Sparks remains untouched by a ligament tear since the inaugural 1997 WNBA season.
While Swoopes serves as an assistant coach and mentor on the bench, 27-year-old Lobo plays sparingly for the Liberty. She scored her first points at the Garden in more than two years during a victory over Seattle on July 11.
Rookies also have endured ligament tears this season. Shea Ralph of the Utah Starzz recently tore her ACL for the fourth time since her freshman year at Connecticut.
Tamika Catchings, who was already rehabbing an ACL injury suffered during her senior season at Tennessee, tore her medial meniscus last month. She was hoping for a late-season debut with the Indiana Fever.
Lobo offers a theory on the rash of knee injuries.
"I just think it's the level that the game is being played at," Lobo said. "It's faster, it's quicker, demanding more from your body. You're leaving yourself more prone to injury.
"But with the way strength training goes in college now and people conditioning their bodies, you'd think it would be the opposite. Unfortunately, that's not the case."