WEST PALM BEACH, Fla. (Cox News Service) -- Osteoarthritis of the knee is more painful and more damaging in smokers, a study reports. Men who smoked had more progressive disease and reported higher levels of pain, a U.S. research team has found.

Millions of people suffer from osteoarthritis, a condition causing inflammation and loss of cartilage in the joints.

The study in Annals of Rheumatic Diseases supports previous research showing smokers feel more back pain than other sufferers.

This pain is not unique to backs, however, although there's a strong relationship with smoking and worsening back pain.

The researchers followed 159 men with symptomatic osteoarthritis of the knee for 30 months. About 12 percent of the participants were current smokers.

MRI scans of the knee showed that the smokers had a more than two-fold increased risk of loss of cartilage in the knee joint -- a process that occurs as the disease progresses.

Men who smoked also had higher pain scores than men who didn't smoke throughout the study. The greater amount of pain was unlikely to be due to increased cartilage loss as cartilage does not have pain fibers, the authors said.

Study author David Felson, professor of medicine at Boston University Medical School, said there were a few potential explanations for the pain finding.

"There is data elsewhere that shows smokers feel more pain.

It's not unique to knees, there's a strong relationship with smoking and worse back pain. My guess is it's a general increase in musculoskeletal pain and that something in cigarette smoke sensitizes people to lower pain thresholds," he said.

Copyright 2006 The New York Times News Service. All rights reserved.