Arch supports may not always protect against knee problems

ORTHOTICS may be as common as water bottles among runners and walkers, but the mass-marketed arch supports may actually increase force on the knee, possibly contributing to knee osteoarthritis, a deterioration of the cartilage.

In a study in this month's issue of Medicine & Science in Sports & Exercise, a group of 22 male and female recreational runners were given basic running shoes (ones with no high-tech structural elements such as shock absorbers). First they ran and walked in just the shoes, then they ran and walked in shoes with over-the-counter cushioned arch support inserts. The runners were analyzed via infrared cameras to track motion of the knee joints. A special treadmill measured forces the runners applied while striding.

The researchers found that during walking, forces on the knee joint increased 6% more with the orthotic than without -- and during running, 4% more. Those differences may seem small, but the repetitive nature of the action and the fact that orthotics may be worn every day troubles the researchers. "We don't want to say that arch support cushions are bad," says study lead author Jason R. Franz, a research engineer at the University of Virginia. But, he says, athletes should not assume over-the-counter orthotics are always beneficial.

jeannine.stein@latimes.com