Experts said other factors could be at work in addition to the overemphasis on leg strength. Advances in magnetic imaging have enabled doctors to see inside the hip and identify certain ailments, and the increasing number of children playing sports at younger ages has led to more instances of improper bone development.

Several of baseball’s biggest stars — including Alex Rodriguez of the Yankees, Chase Utley of the Philadelphia Phillies and Carlos Delgado of the Mets — have been forced to the sideline after having surgery to repair a torn labrum, the cartilage that runs along the rim of the hip socket. Rodriguez recently returned after missing two months, and Delgado has said he may not return this season. On Thursday, one of Utley’s teammates, pitcher Brett Myers, was found to have a damaged labrum in his hip. He is expected to have surgery this week.

Not all doctors are convinced that training is the culprit.

“It’s not like workouts have changed all of a sudden; it doesn’t explain it,” said Christopher Powers, an associate professor of biokinesiology at the University of Southern California. “People and doctors are just more aware of it diagnostically. We’ve always had hip problems; now we are just finding it better.”

The number of players on the disabled list because of hip and groin-muscle injuries rose to 34 in 2008 from 20 in 2007. Through the first quarter of this season, at least 13 players have gone on the disabled list with hip injuries.

“Delgado and A-Rod asked me about it,” said Utley, who had hip surgery last November after the Phillies won the World Series. “They both wanted to know what I did to keep playing.

“Before, guys never had hip surgeries and never let them work on their hips. But this was different.”

No sports medicine experts pointed to performance-enhancing drugs in explaining the rise in hip injuries. But dozens of major league baseball players, including Rodriguez, have been linked to performance-enhancing drugs in recent years, raising suspicions every time a new injury trend appears.

Advertisement Continue reading the main story

“It’s interesting to see what injuries increase as we come out of the steroid era,” said Stan Conte, the head trainer for the Los Angeles Dodgers.

Newsletter Sign Up Continue reading the main story Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up You will receive emails containing news content , updates and promotions from The New York Times. You may opt-out at any time. You agree to receive occasional updates and special offers for The New York Times's products and services. Thank you for subscribing. An error has occurred. Please try again later. View all New York Times newsletters.

The sudden prominence of hip injuries comes a year after an unusual number of baseball players sustained strained oblique muscles, which run from the ribs to the abdomen.

The apparent rash of hip injuries extends beyond baseball, doctors and trainers said. Athletes of all ages and skill levels and in varying sports are having hip problems at higher rates and being found to have labral tears, they said. Soccer and hockey players in particular have followed the conventional training wisdom in recent years and bolstered their knees. Now some of them, including Islanders goalie Rick DiPietro and midfielder Freddie Ljungberg of Major League Soccer’s Seattle Sounders, who have both had labrum surgery, are having hip trouble.

“In soccer, they train harder than they used to train 10 to 15 to 20 years ago, when soccer had had a lot of A.C.L. tears,” said Dr. Andreas H. Gomoll, an associate professor of orthopedic surgery at Harvard Medical School and a surgeon at Brigham and Women’s Hospital.

“They started worrying much more about knees; they now do special training to protect the knee. And one belief is that this is why we have more of these injuries because the strength is putting more pressure on the hips.”

Dr. Bryan T. Kelly, a surgeon at the Hospital for Special Surgery in Manhattan, performed Utley’s operation and is scheduled to operate on Myers. He said he did not believe it was a coincidence that “I get 40 hockey players in a six-week period at the end of the season all coming into my office with the same-looking bone structure in their hips, all saying that they have been skating since they were 3 years old.”

Kelly added, “I believe we are seeing some consequences from having our kids over the past few decades playing sports more at younger ages.”

As magnetic imaging has become more sophisticated, doctors have gained the ability to see inside the hip and identify labral tears.

“We are doing a much better job at imaging the injuries, and we are also seeing athletes with bigger bodies that are working harder on strength and conditioning, and the bigger, stronger muscles are allowing athletes to torque faster and more pressure is being put on the hip,” said Dr. Jordan Metzl, a sports medicine specialist at the Hospital for Special Surgery.

Advertisement Continue reading the main story

Problems with labral tears occur when the head of the femur does not fit correctly in the hip socket. If it is not a good fit, the labrum is squeezed between the ball and the socket when the hip is flexed. Over time, the labrum can become irritated and tear.

The problem with an adolescent, doctors said, is that the head of the femur is still growing. Stress on the hip can cause the bone to become misshapen. As the athlete continues to play sports into adulthood, the improperly shaped bone rubs against the labrum.

“I believe the situation with the hips is similar to Little League baseball, where there is a high awareness to elbow injuries from pitching too much because the joints are still developing,” Kelly said. “But with the hips, nothing is said. There is nothing done to try and prevent damage from being done.”