The painful leg injury plaguing Toronto Raptors star Vince Carter is nothing new and isn't limited to just basketball players.

Dr. Robert Gringmuth, a Toronto chiropractor, said Wednesday he has treated pro soccer players for the injury -- called jumper's knee -- for 16 years.

"I would say, from my experience in pro soccer, we probably have three or four athletes with this per year," said Gringmuth, who began his practice in 1976 and became a sports specialist in 1989.

"It's not as common as things like ankle sprains and muscle strains ... but I do about three to four cases each year.

"I don't see it as a trend. I think I've seen about the same number of cases every year.

"If you check the literature, I think you'll see it was described fairly long ago, like at least 20 to 30 years."

Gringmuth, who didn't want to comment specifically on Carter's condition, has been treating Toronto-based pro soccer players since 1985 and is presently involved with both the A-League's Toronto Lynx and the Toronto ThunderHawks of the indoor National Professional Soccer League.

Carter first suffered his injury Nov. 26 against Chicago and aggravated it early in the first quarter of Toronto's 96-89 victory Tuesday over Philadelphia.

Carter didn't travel with the Raptors, who played in Atlanta on Wednesday.

Instead, he was to undergo tests in Toronto amid fears the injury will force him to miss the Feb. 11 NBA all-star game in Washington.

A club official said Wednesday the Raptors don't expect to learn the results of the tests until Thursday.

Gringmuth said jumper's knee is an inflammation of the tendon that connects the thigh muscle with the kneecap.

It is caused by any activity -- such as jumping and running -- that puts weight-bearing pressure on the muscle and can be quite painful.

Gringmuth said athletes trying to play through the pain risk further injury.

"You could set up a chronic pain cycle where the athlete is unable to shake the pain level that he is experiencing," Gringmuth said. "It sets up a chronic inflammation where certain types of inflammatory cells infiltrate the area and it's very difficult to get them out."

Fortunately, Gringmuth said he has not heard of an athlete requiring surgery as a result of the ailment.

When treating athletes suffering from jumper's knee, Gringmuth recommends "conservative care."

"That would include working on muscles in the area to relax them and make sure they can contract to their optimum and then put them in a strengthening program," he said.

After receiving treatment on his knee Tuesday night, which included ice and strengthening exercises, Carter returned to watch most of the fourth quarter from the Raptors' bench.

Prior to the game, general manager Glen Grunwald said Carter might have to play the remainder of the season in pain, but was hopeful that off-season rehab would provide permanent relief.

Carter led fan voting for the all-star game and is slated to start for the Eastern Conference for the second straight year.

The injury has already prompted Carter to decide against defending his slam-dunk title at this year's all-star weekend.

Carter didn't play in Toronto's 90-80 win in Chicago on Saturday to rest his leg, but resumed practising with the club Monday and appeared fine at Tuesday morning's shootaround.

Earlier this season, he missed five games due to the leg problem.

Carter isn't the only NBA superstar on the limp.

Centre Shaquille O'Neal didn't play in the Los Angeles Lakers' 102-96 win over Cleveland on Tuesday, missing his second straight game with an injured foot.

O'Neal has a tendon ailment in his right arch and is having difficulty pushing off the foot.

He'll travel with the Lakers to Minnesota but was to sit out Wednesday night's game against the Timberwolves.

He's scheduled to visit Dr. Phil Kwong, a foot specialist, and undergo an MRI and CAT scan Thursday.

Injuries have already forced Miami centre Alonzo Mourning (kidney ailment) and Orlando forward Grant Hill (foot) to miss this year's NBA all-star game.

By Dan Ralph