[Hip and knee osteoarthritis. Conventional X-ray best and cheapest diagnostic method].

Osteoarthritis is a multifactorial disease affecting cartilage and subchondral bone. Conventional radiographs are inexpensive and readily available. The hip joint should be examined in weight-bearing with an anteroposterior and a right and left anterior oblique view, rotating the patient 55 degrees in each oblique view. Radiographically established osteoarthritis of the hip is present when the joint space width is less than 3 mm or less than the width in the contralateral hip joint. The femorotibial joint should be examined in a posteroanterior view in weight-bearing and in semiflexion with the central X-ray beam tangential to the medial tibial plateau and with the medial aspect of the foot parallel to the beam. A diagnosis of osteoarthritis of the femorotibial joint is established with the presence of osteophytes at the medial or lateral aspect of the joint. Joint space narrowing with a joint width less than 3 mm is a sign of severe disease. The femoropatellar joint should be examined in skyline view in standing with the X-ray beam parallel to the articular aspect of the patella. A diagnosis of osteoarthritis of the femoropatellar joint is established with a joint space width less than 5 mm. Conventional radiographs of the hip and knee joints are believed to remain the primary examination for detecting signs of degenerative disease in these joints, although MRI is a superior technique for revealing even small areas of degenerative changes.