By last December, Scott Tinley's hip hurt so bad that the 49-year-old, two-time Ironman World Champion walked with a noticeable limp, had a hard time bending over to tie his shoes and hadn't run in five years.

Last summer, after dragging her right leg sideways "like a crab" for two years and having it repeatedly buckle beneath her at the world championships in Scotland, adventure racing superstar Robyn Benincasa, 41, got an X-ray and some bad news.

"You've got end-stage osteoarthritis in your hip - no cartilage, bone-on-bone," said her doctor. "Unless you like running in extreme pain, your athletic career is over."

A year ago, 51-year-old Beverly Hills trainer-to-the-stars Gary Kobat, a world-class age-group duathlete who has run 51 marathons, frantically tried massage, chiropractic, Rolfing (a system of soft tissue manipulation, with the objective of realigning the body structurally and harmonizing its fundamental movement patterns in relation to gravity) and various forms of bodywork to relieve the excruciating hip pain that had ended his running.

"Your only option for a normal life is a total hip replacement," said a surgeon who, as a Spinning-class client of Kobat's, offered to do it for free. But Kobat turned down the gift because it wouldn't leave him "normal" as he defined it.

A traditional hip replacement lasts only 10 years and is recommended for low-activity people over age 60. That's because it is not strong enough to handle serious athletic activity, like long-distance running.
No more running - a thought that is chilling to the millions of people over the last couple of decades who have made mega-mile fitness part of their lives and livelihoods.

"I thought, ‘What if I'll never be what I was again?'" says Benincasa, a former child gymnastics star and 1998 National Judo Champion who has run up to 70 miles a week for three decades and has completed hundreds of marathons and adventure races along with nine Ironman triathlons, including four Ironman World Championships in Hawaii.

"What if I can't do a 10K? What if I can't hike to Machu Picchu? Oh my god," she remembers screaming to herself. "This is the end of my athletic career!"
But that was then.

In March, Benincasa ran a marathon, Kobat was doing track workouts of four one-mile repeats at 5:45 pace, and Tinley was surfing and planning to run by July. The reason: hip resurfacing, a new medical procedure with state-of-the-art technology that promises to rewrite the rules of athletic longevity. Untily recently, the procedure was relatively unknown in the United States.

Hip resurfacing is a procedure that literally resurfaces the worn-out ball-and-socket structure of the hip with steel. The operation cuts a six-inch gash in your buttock and installs a finely honed cobalt-chromium steel cap and cup that slide smoothly on one another, assisted by synovial fluid that leaks in from the surrounding bones.

In a damaged hip, the slick, lubricated hyaline cartilage that once coated the rounded head (the ball) of the femur (the thighbone) and the cup-like acetabulum (the socket) of the pelvis has deteriorated, leaving the bone-on-bone surfaces painfully grinding on each other and reducing range of motion.

"A 45-year-old person with bone-on-bone is miserable - he's disabled but not ready to sit down yet," says Dr. John A. Rogerson, who has done about 300 of the surgeries at Meriter Hospital in Madison, Wisconsin, since the FDA approved it in May 2006, including Tinley's in December. He expects to do thousands more, because bad hips are now showing up earlier in individuals.

"In the past, arthritic hips didn't appear until later in life," says Dr. Rogerson. "But now there's a whole new demographic: those who have been extremely active through their 20s, 30s and 40s."

Reasons for the deterioration can be osteoarthritis, occurring in people 45 and older and caused by a combination of overuse and imbalances; rheumatoid arthritis, an immune-system foul-up in which the body attacks its own cartilage; and trauma from a fall or accident, which may lead to avascular necrosis, the weakening and eventual collapse of bones due to lack of blood supply.

The latter happened to Floyd Landis, the drug-deposed ex-winner of the 2006 Tour de France. He had a hip resurfacing operation in late 2006 and last summer took second place in the 100-mile Leadville 100 mountain bike race.