Over 40 years, Bob Niebuhr learned that handball doesn't have to be a young man's game — that an old man can deliciously keep a young man running around the court by swatting the ball with the proper power, precision and geo­metry. So when Niebuhr, 68, saw the doctor last week for a checkup after his second hip replacement, he had one burning question:

"How about handball?"

Niebuhr's passion helps explain the explosive growth of Twin Cities clinics specializing in orthopedics and sports medicine. Minnesota has seen some $66 million in capital projects related to orthopedic care between 2008 and 2012.

And it is why the Mayo Clinic — after years of flirting with a medical presence in the Twin Cities — broke through last week with the announcement of a downtown Minneapolis sports medicine center in league with the Minnesota Timberwolves.

"The growth is being driven by a more active population, whether that happens to be in competitive sports or fitness activities," said Dr. Michael Stuart, co-director of the Mayo Clinic Sports Medicine Center, who is in Sochi now as team doctor for USA Hockey. "I have a 65-year-old patient who plays 120 softball games a year."

Across the Twin Cities, orthopedic clinics report booming business.

At St. Croix Orthopaedics in Stillwater, visits to urgent care more than doubled from its first year, 2012, to last year. At the TRIA orthopedic center in Bloomington, half the injury patients are athletes — many of whom line up at the walk-in clinic in football pads or jogging outfits.

"You walk over to our acute injury clinic, and you will see athletes with three or four different letter jackets on," said Ted Wegleitner, TRIA's chief operating officer.

The growth appears at the margins of the age spectrum, with children suffering the breaks and strains of high-level sports participation, and older adults wearing out joints after decades of running, biking or — in Niebuhr's case — lunging after rubber balls.

"It was hard to turn my hips, and it was painful to hit the ball and follow through and to move," said Niebuhr, who learned handball at college in La Crosse, Wis. "When you play you're moving side to side, up and back, diagonally, you know? I would move back and really feel it."

'Will I be able to ski?'

Sports has always been a seductive market for business — sometimes to excess, considering reports that the Twin Cities area is oversaturated with golf courses and sports training domes.

The key question is whether Mayo's venture will cater to an expanding market of athletes, young and old, or just intensify competition in a community where TRIA, Twin Cities Orthopedics, Summit Orthopedics, the University of Minnesota and St. Croix are among the major players.

The growing intensity of youth sports has contributed to the trend, as children specialize in their chosen sports and become prone to overuse injuries, sprains and concussions.

Stuart said there has been "quite an epidemic" of young female athletes with disruptions to their anterior cruciate ligaments, the so-called ACLs that regulate knee motion.

But it is the size and attitude of the baby boomer generation that have orthopedic center leaders confident there will be enough patients to go around. The Greatest Generation of adults, born in the first half of the 20th century, might have accepted the need to slow down, but the boomers born in the 1950s and 1960s have not, said Dr. David Fischer, an orthopedic surgeon who co-founded TRIA in 2005.

"Where our parents would have accepted a bad knee and changed their activities, this population in large part doesn't want to do that," he said. "They're asking 'Will I be able to play tennis? Will I be able to ski?' "

Generally, he added, their expectations are "reasonable."

Dr. Michael Meisterling of St. Croix Orthopedics winced after his patient, Niebuhr, asked about handball after two hip replacements. But the doctor told him he could slowly return to the sport, though it might wear out his new implants.

"The new hips have a 25-year shelf life," Niebuhr said. "In 25 years, I'll be 94 years old. If I'm still playing handball and I need a new hip when I'm 94, I'll go for it."

In reality, Niebuhr plans to back off handball just a bit — there's always golf and sledding with his two grandchildren.

The rise in obesity has also contributed to the increase in joint problems — sometimes in combination with athletics as people exercise to lose weight.

Every 15 pounds of excess weight puts 100 pounds more pressure on the body's joints, said Melanie Sullivan, chief executive officer for St. Croix Orthopaedics.

"If you're 45 pounds overweight, your force is 300 pounds more than what you would normally put on your joints."

Training like a pro

Already, the clinics are competing for patients. TRIAL and Twin Cities Orthopedics duel for patients with facilities and walk-in clinics that are 2 miles apart on France Avenue. The Mayo Clinic Sports Medicine Center, which will open in 2015 across from Target Center, will include some form of walk-in clinic that will concentrate on downtown dwellers and commuters, Stuart said.

"There are a lot of people that work downtown," he said, "and they don't have this type of convenient opportunity to be evaluated, treated, rehabbed by any facility that is connected by skyway to … their offices."

Aligning with high-profile sports teams can be a marketing advantage. TRIA's Fischer has been team doctor for the Timberwolves since the team's inception in 1989. Mayo announced it will be taking on that role.

That kind of relationship wasn't lost on patients such as Scott Weyer, 67, of Prior Lake. While he researched the volume and quality of knee procedures at facilities as well, he was first drawn to TRIA because it treated athletes from the Twins, Wild and Vikings.

"You hear about these players that get this done to them and that done to them, and then they're back on the field," said Weyer, who wanted a knee procedure to stay mobile at his manufacturing job and on hiking trips with his wife. "I figured these guys must know what they are doing."

In addition to surgery and injury treatment, clinics are creating programs to help athletes prevent injuries and physical therapy to help them recover after an operation. TRIA's physical therapy program has grown 45 percent in three years, and it recently added equipment such as baseball netting so therapists can work with players on throwing mechanics.

Mayo will emphasize prevention and athletic performance as well, Stuart said.

"Athletes are looking to improve their strength and balance and conditioning — and how to think the game as well as reaction time and vision and nutrition," he said. "Elite athlete are really looking for that kind of improvement, but so are a lot of competitive and recreational athletes."

Jeremy Olson • 612-673-7744