Known risk factors for knee OA include a history of trauma, a family history of the disease, certain metabolic conditions, and obesity.

A recent study has confirmed the suspicion that smoking has another detrimental effect on health. It can worsen the prognosis of men who have osteoarthritis of the knee. The study, performed by researchers from Boston University School of Medicine and the Mayo Clinic and published in the January 2007 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.

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 stated.

"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.

One hypothesis is that smoking may ?turn on? proinflammatory mechanisms in osteoarthritis. This may occur as a result of the interaction of nicotine or other ingredients and predisposing genetic markers a patient may possess.

(Interestingly, cigarette smoking also is a risk factor for rheumatoid arthritis and the turning on of proinflammatory cytokines is felt to be cause).

It is critical for patients to understand the need to reduce any risk factors for arthritis they may have. For instance, if a patient already has a strong family history of osteoarthritis, they may want to avoid cigarette smoking altogether.

Add this potential medical problem to the long list of things that smoking aggravates.