Ultrasound of the joints.

High-frequency ultrasound is now considered an excellent modality to image normal tendons, muscles, and peripheral nerves as well as to diagnose a wide variety of pathological conditions affecting these structures. Although US is limited in the visualisation of some intra-articular structures, it can be a useful tool in joint disease assessment. Ultrasound has some advantages over other imaging modalities including time- and cost-effectiveness, superior spatial resolution, dynamic examination and the possibility to perform the examination in a comfortable position for the patient. The aims of this review are twofold: firstly, to present the normal US appearance of the joint structures that are susceptible to US examination, including the joint surfaces, intra-articular structures such as menisci and other fibrocartilages, capsule and ligaments; and secondly, to show the US appearance of the most commonly encountered joint disorders and discuss the role of US in the imaging strategy of joint disorders.