Ultrasound-guided injection and aspiration of small joints: techniques, pearls, and pitfalls.

Ultrasound (US)-guided musculoskeletal intervention of small joints or joints other than the shoulder, elbow, hip, knee, and ankle can be technically challenging. Small joints produce a narrower landing zone for the needle and a smaller target that may be made even more inaccessible by bulky osteophytes. Sonographic (US) guidance offers important advantages including near-field visualization of the joint and soft tissues, ease of access, portability, ability to compare with the contralateral side, and lack of ionization radiation. This review article focuses on the performance of US-guided injections and aspirations involving small joints (joint capacity < 2 mL and/or typically evaluated or injected with a compact linear transducer). For each joint (temporomandibular, acromioclavicular, sternoclavicular, distal radioulnar, symphysis pubis, and joints of the digits of the hands and feet), a brief overview of the relevant anatomy, indications, procedural description, pearls and pitfalls will be highlighted. This article demonstrates the various approaches to diagnostic or therapeutic injection and aspiration of small joints with the aid of US images, cines and graphic illustrations, emphasizing joint positioning, anatomic landmarks, and needle trajectory for a safe and efficacious procedure. A brief review of available literature for each joint will also be provided.