Sonography is currently being applied to many areas of the musculoskeletal system. Although some areas are in the experimental stage, there exist several indications in which sonography can produce results at least equal to what is possible with MR imaging. Examples include evaluation for shoulder and ankle tendon abnormalities; soft tissue infection and joint effusion; soft tissue foreign bodies; soft tissue masses, such as Baker's cyst and wrist ganglion cyst; carpal tunnel syndrome; developmental dysplasia of the hip; and other indications where MR imaging is contraindicated. The role of sonography in evaluation of the musculoskeletal system is evolving. With continued experience and research, newer applications for musculoskeletal sonography will likely become established further defining the roles of sonography and MR imaging in evaluation of the musculoskeletal system.