The most recommendable MRI sequence for the morphologic assessment of the cartilage damage due to osteoarthritis (OA) is gradient echo fat suppression T1 weighted image (SPGR: Spoiled gradient recalled acquisition in the steady state, FLASH: Fast low-angle shot). For the detection of the cartilage degeneration before the morphological change, T2 mapping, dGEMRIC (delayed Gd-DTPA2-Enhanced MRI of Cartilage), and T1ρ mapping are suggested. Subchondral bone structural changes such as bone sclerosis and cyst are deeply related to the etiology of OA, and quantitative evaluation for them using MDCT (Multi-Detector row CT) and 3TMRI are suggested.