Osteoarthritis of the knees. X-rays of a section through the knees of a 65-year-old patient with osteoarthritis affecting both knee joints, showing the kneecaps (upper left and right). Osteoarthritis (or arthrosis) is a common degenerative disease characterised by a loss of the cartilage that lines the joints between bones. This leads to pain, swelling and occasionally may result in the loss of function of the affected joint. No specific cure exists.