For overweight people hobbled by knee arthritis, losing even one pound can diminish the stress the knees take with every step, a new study shows.

The study, of 142 overweight adults with knee arthritis, found that for each pound participants were able to shed, there was a 4-pound reduction in the force hitting their knees with every stride they took while walking.

That, according to the researchers, means that dropping just one pound would reduce the "load" on the knee joint enough to translate into slower arthritis progression.

Excess weight can contribute to the both the development and progression of knee osteoarthritis. The most common form of arthritis, osteoarthritis occurs when the cartilage cushioning the joints breaks down over time, causing inflammation, pain and stiffness.

Experts recommend that overweight and obese adults with knee arthritis lose weight and exercise to help manage the condition. But whether weight loss actually slows the progression of knee arthritis is not yet clear, Dr. Stephen P. Messier of Wake Forest University in Winston-Salem, North Carolina, and colleagues note in the journal Arthritis & Rheumatism.

In their study, the team tried to gauge the effects weight loss can have on arthritis patients' knee mechanics. The participants, all older adults with disabling arthritis symptoms, were part of a larger weight-loss study.

The researchers performed a "gait analysis" of each patient at the beginning of the study, and 6 and 18 months later. As mentioned, they found that for each pound participants lost during that time, there was a four-fold greater reduction in the force going into the knee with each step they took.

"Accumulated over thousands of steps per day," the investigators write, "a reduction of this magnitude would appear to be clinically meaningful."

A "critical question," they add, is whether such weight-loss effects hold up over time, and whether they can slow the progression of knee arthritis.

SOURCE: Arthritis & Rheumatism, July 2005.