Over-exercising is not a major factor in causing arthritis, according to one health expert.

Jane Spence, spokesperson for the support group Arthritis Care, hit out against claims made by researchers at the Radiological Society of North America that middle-aged men and women who engage in high levels of physical activity may unknowingly cause damage to their knees and increase their risk for osteoarthritis.

"Over exercising itself isn't generally the issue," Ms Spence asserted.

"It is more that if you damage your joints by repetitive or high impact physical activity, it is common to develop arthritis at the injury site as a result later on."

In addition, it is not usually the amount of fitness training but the type which can cause damage to the joints Ms Spence continued.

She advised that the risk of secondary arthritis can be reduced by avoiding the joint damage caused by high impact sports, repetitive physical work, or wearing high heels or shoes which lack good foot support.