[Magnetic resonance (MR) imaging of the shoulder, elbow, and wrist]

Thorough knowledge of small structures in the joints is becoming important as the resolution of magnetic resonance (MR) imaging has improved during the past decade. The author discusses the MR anatomy and pathology of three representative structures in the joints of the upper extremities: the labral-ligamentous complex of the shoulder, ulnar collateral ligament(UCL) of the elbow, and triangular fibrocartilage complex(TFCC) of the wrist. The labral-ligamentous complex is composed of the anterior labrum and three glenohumeral ligaments. Because of their similar MR appearance, the labral sulcus is difficult to differentiate from traumatic detachment of the labrum, even with the aid of MR arthrography. Insertion of the UCL to the medial condyle in the growing elbow presents different MR appearances according to age. Acute and chronic UCL tears are commonly seen in elbows with medial tension overload and are well depicted with three-dimensional Fourier transform(3DFT) gradient-echo images. 3DFT images are the most suitable for observation of the TFCC as well. Since abnormally high signals of the articular disc suggestive of tear are often seen in asymptomatic subjects, MR imaging may not reliably be used to differentiate clinically significant tears from asymptomatic defects. In this review article, the author emphasizes developmental anatomy and normal variations in the interpretation of MR images.