Frontal X-ray of a 71-year-old female patient with diffuse bone demineralization and osteoarthritis of the right knee. 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. A discreet external tilt of the kneecap is also seen.