Wedge insoles made of a rubbery sponge material were used in a study of patients with uneven wear of the knee from osteoarthritis. Dr. Toda teamed up with a physical therapist and a nurse to try the insoles with 62 women in three age groups.

Three sizes of wedges were used. They found the biggest wedge gave the best correction of ankle and knee angle, but it was the most uncomfortable. A lower wedge (eight or 12 mm) works well for regular day-to-day use. Sponge rubber was used at first, but the researchers switched to urethane foam, a softer blend of plastics.

The researchers reported the best tilt of the wedge may be decided by the patient's age. Older patients may need a lower tilt. Muscle weakness in the lower leg may interfere with the wedge working well. Because problems can occur, it's best to work with a physical therapist and an orthotist (someone trained in specialized shoe inserts) instead of buying something off the shelf and treating yourself.