Musculoskeletal conditions account for about one-quarter of U.S. short-term disability claims, an insurer says.

Researchers in the Simsbury, Conn., life offices of Hartford Financial Services Group Inc. (NYSE: HIG), base that figure on an analysis of about 750,000 STD claims.

Men were more likely to submit claims for back and spine problems, and women were more likely to submit claims for problems with ankles and feet.

About 25% of the STD claims were due to worn-out spinal discs, and about 20% were due to knee problems related to arthritis or worn-out cartilage, Hartford says.

The average musculoskeletal STD claim led to 10 weeks of time off work, Hartford says.