Magnetic resonance imaging (MRI) provides an excellent soft tissue contrast with high spatial resolution. Using spin echo and fast gradient echo sequences all relevant joint structures such as the hyaline cartilage, the meniscus, the ligaments, the tendons, the capsulae, and their adjacent muscles and their pathology are visualized. Diagnosis of osteonecrosis, meniscal and cruciate ligament lesions, as well as tumors, represents the major current indication for MRI. Due to its high cost MRI should be employed for the diagnosis of joint disease only to clarify equivocal findings of conventional radiographic, nuclear and tomographic methods. Prior clinical examination and laboratory tests are mandatory. As a component of a stepwise diagnostic approach, MRI often provides reliable differential diagnostic information.