This chapter discusses the techniques, pathology, and potential pitfalls involved in the use of musculoskeletal ultrasound in the emergency department (ED). It reviews the sonography features of tendons, muscles, bone, joints, ligaments and nerves, and specific imaging techniques. Although fractures are typically diagnosed in the ED by radiography, there is a role for ultrasound in diagnosing fractures. Sonography is very accurate in detecting fractures of the humerus, midshaft femur, radius/ulna, and tibia/fibula. To evaluate the humerus, the transducer should be placed over the distal humerus anteriorly. Imaging of the femur should begin at the distal femur by placing the probe superior to the patella over the thigh laterally. Rib fractures are often difficult to detect on radiographs. In the case of a suspected rib fracture, ultrasound can be used to confirm the diagnosis. Sonography also has a role in identifying and assisting with the aspiration of joint effusions.