TORONTO -- It seems somewhat ironic, but the exercise regime often recommended by doctors and therapists as a rehabilitation tool to overcome a range of sports injuries can itself be a cause of harm.

Yoga, considered a relatively gentle means of building flexibility, muscle strength and endurance through physical poses and controlled breathing, can lead to a number of repetitive strain injuries and even osteoarthritis, doctors say.

"Most of the injuries I see are from repetitive strain," says Dr. Raza Awan, a Toronto sports medicine physician who's been practising yoga for about a decade.

The most common yoga-related injuries he sees in patients are rotator cuff tendonitis and tears; spinal disc injuries in the low back and neck; cartilage tears in the knee; hamstring strain and tears; and wrist injuries.

There are a number of reasons why yoga -- in which practitioners generally perform a series of poses, called asanas -- can cause injury, he says.

One reason is "definitely pushing too hard" to attain a specific pose, which can involve stretching the upper body into a forward or backward bend, twisting the torso, or performing an inversion, such as a handstand or headstand, balanced on the hands or forearms.

"So, for instance, people who are too flexible or people who are too tight, they're at more risk, I find," says Awan. "If you're too tight and you try to force yourself into a pose and your muscles aren't flexible, then you might strain another area to compensate."

"Or let's say that you're very flexible and you get to the end range of a pose and you don't have the muscular support to maintain the pose ... you're holding the pose without muscular endurance, you're basically holding it on your ligaments or your tendons and you strain those structures that way."

Ego also can lead to injury, he says, explaining that in yoga classes, some people will push their body beyond its limits trying to match or outdo the person on the next mat.

Even competing with oneself -- for instance, trying to get the heels flat to the floor during the "downward dog" pose, despite having tight calf muscles from sitting at the computer for hours -- can lead to strains or tears, he says.

"You strain yourself because you push yourself."

Sometimes, overdoing it in yoga may exacerbate an underlying problem called femoroacetabular impingement, or FAI, in which the bones of the hip are abnormally shaped and don't move together smoothly. The hip bones grind against each other during movement, causing the joint to be damaged over time and osteoarthritis to set in.

Dr. Chris Woollam, a Toronto sports medicine physician, says he started seeing "an inordinate number of hip problems" about two years ago, including among women aged 30 to 50 who were practising yoga.

When range of motion in their hips was tested, not only were the limits of movement diminished, but "they would jump off the table because of the pain," Woollam says.

MRI scans showed the women had joint damage resulting from femoroacetabular impingement, which can in some cases require hip-replacement surgery.

"So maybe these extreme ranges of motion were causing the joint to get jammed and some to wear," Woollam says. "If you start wearing a joint down, then it becomes arthritic. So you're seeing these little patches of arthritis in an otherwise normal hip that seem to be related to these extremes of motion or impingement or both."

That appears to have been the case for Cory Lund, a Toronto artist who started doing yoga about 20 years ago -- after he injured his back in a snowboarding accident and found the stretching exercise helped alleviate the pain better than anything else he tried.

Over the years, he practised different kinds of yoga, most recently one called ashtanga, a more vigorous type that involves moving through a series of progressively challenging poses.

But about 18 months ago, Lund began experiencing periodic bouts of nagging hip pain, which was diagnosed in his right hip as FAI.

"It is an injury and I know that now, but it's not like there was some catastrophic moment," says Lund, who is currently taking a hiatus from yoga.

"My body can only do what it does and the whole point of yoga is to respect its limits. I'm not a terribly flexible person ... When I moved into the positions that are the end range of motion, it has caused damage," he says.

"Yoga isn't entirely to blame. You just have to listen to your body. When it's saying there's a pain, then you have to recognize that."

Awan believes most yoga-related injuries are preventable.

"There's a lot of benefits to doing yoga for certain types of problems, but obviously any physical activity has its risks, too," he says.

"It's a great movement-based activity to do, but you have to try to keep safe, just like in other sports activities. Don't push your body beyond."