Middle-aged people who do large amounts of exercise may increase their risk of needing knee replacement surgery, experts have claimed.
According to scientists at the University of California, San Francisco (UCSF), high levels of physical activity may heighten the chances of developing knee osteoarthritis, for which joint replacement surgery is an increasingly common treatment.
The team studied 236 patients, none of whom suffered from knee pain or were overweight.
MRI scans revealed that those who did the most exercise tended to have the most severe knee damage.
The findings were presented at the annual meeting of the Radiological Society of North America by Dr Christoph Stehling, from the UCSF department of radiology and biomedical imaging.
"Our data suggest that people with higher physical activity levels may be at greater risk for developing knee abnormalities and, thus, at higher risk for developing osteoarthritis," he revealed.
"The prevalence of the knee abnormalities increased with the level of physical activity."
Over 30,000 knee replacement operations are carried out each year in England and Wales, according to the Arthritis Research Campaign.
The procedure provides relief from pain and improves mobility, with around four-fifths of recipients claiming to be happy with their new knees.