March 13 (HealthDay News) -- Losing weight may not help prevent the progression of knee osteoarthritis, a new study suggests.

Researchers looked at more than 2,600 people with the knee ailment who were at high risk for the condition because they were overweight or obese or had other risk factors such as knee pain or previous knee injuries. Participants were given a physical examination and hip bone mineral test and had X-rays taken of both legs at the start of the study and of their knees again after 30 months.

The study found that obesity did increase the risk of knee osteoarthritis but that weight had no overall effect on the likelihood of the disease progressing, said D.T. Felson, of Boston University School of Medicine, and colleagues.

However, the researchers did find that weight had an effect on progression depending on how the knees were aligned. People with high body mass index and neutral alignment had an increased risk of progressive knee osteoarthritis, those with valgus (knock-kneed) alignment had a small risk and people with varus (bowlegged) alignment had no increased risk.

Among participants who did not have knee osteoarthritis, obesity increased the risk of developing the disease, regardless of their knee alignment.

"The failure to demonstrate that obesity increases the overall risk of [osteoarthritis] progression in our study and others does not eliminate opportunities for weight loss trials aimed at slowing disease progression, especially among knees in extremities with neutral or valgus alignment," the researchers wrote.

The study was published in the March issue of the journal Arthritis Care & Research.

SOURCE: Wiley-Blackwell, news release, March 3, 2009