Dr. Nabil Bissada of Case Western Reserve University in Cleveland said bacteria might link the mouth and the knee.
Bissada and colleagues analyzed data on 36 patients with gum disease and arthritis of the knee. In about 15 percent of the patients, researchers found the fluid that lubricates the knee had bacteria with the same DNA as the mouth plaque.
Bissada said he suspects gum inflammation let the bacteria get into the bloodstream and wind up in the knee, where he thinks it could cause problems for arthritis patients.
"The easiest way is to minimize that risk by treating gum disease, or even better, preventing gum disease," Bissada said in a statement.
The study was published in the Journal of Clinical Rheumatology.