The man fractured the thighbone on his right leg while doing a difficult seated yoga pose known as Marichyasana posture B in his morning yoga class, according to a report of the man's case published in the journal BMJ Case Reports.
The pose involves sitting down, with the knee bent and drawn up to the chest, and then bending the torso toward the floor.
When the man got into the position, he heard a loud cracking sound and felt enormous pain in his right femur (thighbone). The pain caused him to collapse on the ground and an ambulance took him to the hospital.
The man's right thighbone was fractured about 4 inches above his knee joint, said Dr Andrew Moriarity, an orthopedic resident at St James's Hospital in Dublin, Ireland, who treated the man and co-authored the case report.
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Although yoga, an ancient Indian meditative practice, is considered a gentle mind-body practice, injuries can and do happen, especially as the activity's popularity rises.
Still, this type of fracture is extremely rare in a young, healthy person, and it's even more unusual for it to occur due to yoga, researchers said in their case report.
Two weeks before the fracture occurred, the man felt a dull pain in his right thigh. He sought advice about the problem from a physical therapist, who diagnosed it as a muscle strain in the man's quadriceps, telling him he could return to yoga.
That probably wasn't a good idea, Moriarity said.
"The pain he felt in his thigh was likely a stress fracture, a warning of impending fracture if he continued to apply stress to this area," Moriarity said.
The reason this man sustained such a rare injury from practicing yoga, Moriarity said, "was likely due to repetitive stress on the thighbone, combined with a weakened bone state, known as osteopenia."
A bone scan taken at the hospital showed that the man did indeed have osteopenia, a condition in which his bone density was lower than normal, which could increase his risk for low-energy fractures, Moriarity said.