Smoking may increase the risk for cartilage loss and more severe pain in men with osteoarthritis of the knee, according to a new study.

The study, by researchers from Boston University School of Medicine and the Mayo Clinic and published in the January issue of the Annals of the Rheumatic Diseases, followed 159 men with knee osteoarthritis for 30 months. Nineteen of the men were smokers.

After the researchers adjusted their study results for age, body mass index (a measure of weight in relation to height) and baseline cartilage scores, they found that the smokers were at increased risk of cartilage loss and experienced more pain than the men who did not smoke.

"Our findings also suggest smoking plays a role in the progression of symptomatic knee osteoarthritis and, therefore, is a modifiable risk factor with important public health implications," Dr. David Felson, director of the Clinical Epidemiology Research and Training Unit and professor of medicine and public health at Boston University School of Medicine, said in a prepared statement.

The researchers could not pinpoint why smoking was associated with knee pain. It is not likely due to cartilage loss, since cartilage does not have pain fibers, Felson explained.

"Instead, smoking may have direct effects on other articular structures mediating knee pain or may modify the threshold for musculoskeletal pain among smokers," he said.

Further study is needed to investigate the effects of smoking on knee osteoarthritis, the researchers added.