Participants were weighed and underwent knee X-rays for signs of cartilage loss.
An average of nine years later, they were assessed again for symptoms and radiographic signs of OA, as well as weight.
Of the knees showing risk of OA on X-ray at baseline, 9.5 per cent developed incident disease by follow-up. Of those showing symptomatic risk, 7.2 per cent developed OA.
But recreational walking, jogging or other self-reported activity had no effect.
This remained the case regardless of the level of physical activity undertaken, even in overweight individuals at increased risk.