Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field rather than x-rays to provide clear and detailed pictures of internal organs and tissues. The parts of the musculoskeletal system that are most frequently imaged with MRI are the spine, knee and shoulder. However, MRI has also been used to study almost every joint in the body including the hips, wrists, and hands. MRI requires specialized equipment and expertise and allows evaluation of some body structures that may not be as visible with other imaging methods.

Because MRI can give such clear pictures of soft tissue structures near and around bones, it is usually the best choice for examination of the body's major joints, the spine for disk disease and soft tissues of the extremities. MRI is widely used to diagnose sports-related injuries, as well as work-related disorders caused by repeated strain, vibration or forceful impact.

Using MRI images, physicians can locate and identify the cause of pain, swelling or bleeding in the tissues in and around the joints and bones. The images allow the physician to clearly see even very small tears and injuries to tendons, ligaments and muscles and even some fractures that cannot be seen on x-rays.

In addition, MRI images can give physicians a clear picture of degenerative disorders such as arthritis, deterioration of joint surfaces, or a herniated disk. Neurosurgeons often use MRI to evaluate the integrity of the spinal cord after trauma.

Finally, MRI is also useful for the diagnosis and characterization of infections (osteomyelitis for example) and tumors (metastases for example) involving bones and joints.

Bone is better imaged by conventional x-rays and CT is preferred for unstable patients with severe bleeding. MRI may not always distinguish between tumor tissue and edema fluid, and does not detect calcium when this is present within a tumor. In most cases the exam is safe for patients with metal implants with the exception of a few types of implants, so patients should inform the technician of an implant prior to the test. The exam must be used cautiously in early pregnancy. The presence of a pacemaker precludes the use of MRI.