Three areas of functional anatomy are present in the distal ulna. Each of these has a specific function in load bearing of the wrist, rotation of the forearm, and maintenance of the relationship between the radius and ulna. The distal portion of the ulna serves as a suspensory post for ligaments that stabilize the ulnar border of the wrist. The midportion of the distal ulna contains the load-bearing triangular fibrocartilage complex. The proximal portion of the distal ulna articulates with the radius at the sigmoid notch and participates in forearm rotation. Each of these areas is assessed in problems related to ligament instability, load bearing, and range of motion. Mechanical problems that affect the distal joint of the radius and ulna include the affects of trauma, degenerative change, and inflammatory disease. Each of these requires evaluation in the treatment of joint derangement. Diagnostic studies that relate to problems in the distal radioulnar joint area include standard roentgenographs, arthrograms, magnetic resonance (MR) scanning, and arthroscopy. Each of these studies has particular advantages and disadvantages in providing data for analysis of joint malfunction. A medical history, physical examination, and use of proper diagnostic studies will assist in an appropriate diagnosis of problems in the distal joint of the radius and ulna.