Plain radiography remains useful for the diagnosis of osteoarthritis, even if it is not always essential. It is moreover poorly correlated with symptoms, as it reflects rather the accumulation of damage then active processes. Similarly, it is a poor indicator of the progression of osteoarthritis. Modem imaging, particularly MRI, has allowed us to understand better the evolving processes, demonstrating a good correlation with symptoms and a better predictive value of clinical course. It has gradually replaced standard radiography in the study because it directly demonstrates sequelae and the active processes in all the structures of the joint. It remains clinically indicated only to exclude an alternative diagnosis or to determine a possible complication of osteoarthritis.