A major role in imaging of the locomotor apparatus. Today, magnetic resonance imaging (MRI) has replaced invasive explorations such as arthrography or saccoradiculography. However, x-rays and scans must often be performed beforehand. Indisputable indications. MRI is crucial in affections of the spongy bone (tumours, osteonecrosis, algodystrophy, fatigue fractures.) and the soft parts (tumours, myositis, fasciitis.). Depending on the situation. The indications for MRI must be weighed versus a scan or arthro-scan in many situations. In the case of strong suspicion of an internal articular disorder, the arthro-scan currently more precise must be preferred. In cases in which there is little clinical orientation, the MRI is justified because of its capacity for global articular and abarticular exploration.