A 62-year-old woman presented with bilateral knee crepitus, swelling and stiffness. Radiographic examination reveals bilateral chondrocalcinosis. (Figures A and B) DIAGNOSIS: Calcium pyrophosphate dihydrate (CPPD) deposition disease; also known as pseudogout. SOME POINTS TO REMEMBER ABOUT CPPD: • infl ammatory joint disease resulting from deposition of calcium pyrophosphate dihydrate into the synovial fl uid; a metabolic disturbance in which there is an impaired degradation or excessive production of pyrophosphate • may be acute (more prevalent in males) or chronic (more prevalent in females) • frequently associated with diabetes mellitus • features include articular cartilage calcifi cation, with possible periarticular calcifi cation of synovium, articular capsule, tendons, bursae • affected hyaline cartilage appears as a fi ne radiopaque line parallel to the contour of the articular cortex • affected fi brocartilage demonstrates a characteristic punctate calcifi cation • in the knee, the menisci classically demonstrate calcifi cation • joint destruction associated with CPPD is virtually indistinguishable from that of osteoarthritis • CPPD also tends to affect the shoulder, elbow, radiocarpal joint, hip, symphysis pubis and patellofemoral joint • joint aspiration may be necessary to confi rm the diagnosis