Osteoarthritis is the most common degenerative joint disease, occurring when cartilage lining the ends of bones breaks down. Sufferers experience inflammation, pain, and progressive loss of function in the affected joints.

Researchers had believed such inflammation arose solely from bits of joint cartilage breaking off and aggravating the synovium -- the thin, smooth membrane lining a joint. But Professors Dennis McGonagle of the University of Leeds and Michael Benjamin of Cardiff University suspected the attachment sites of ligaments and tendons to bone could also be an important factor in joint inflammation.

They examined ligament and tendon attachment sites in the preserved joints of 60 cadavers with a mean age of 84 years at death and found degenerative changes at 76 percent of the attachment sites, and evidence of inflammation at 85 percent of the sites.

The researchers also found 82 percent of the ligament and tendon attachment sites derived nourishment from the synovial joint tissue, so that inflammation at attachment sites could readily affect joints.

The findings appear in the journal Arthritis & Rheumatism.