Magnetic resonance imaging (MRI) can image all the tissues involved in the osteoarthritic joint-not just the cartilage but also the ligaments, synovium, menisci and subchondral bone. Despite these abilities, MRI does not have an established place in the investigation or management of osteoarthritis (OA). This chapter will overview the literature concerning MRI abnormalities in OA, and their relationship to structural progression and symptoms, in order to let the reader decide on the benefits of MRI in their particular practice. The evidence reviewed here will relate to knee OA, reflecting the vast preponderance of MRI studies in the knee.