Radialulnar

Radialulnar refers to the forearm relationship between the radius and ulna, including the proximal radioulnar joint (PRUJ) near the elbow, the distal radioulnar joint (DRUJ) near the wrist, and the interosseous membrane that binds the two bones along their length. Stabilization is provided by the annular ligament around the radial head and by additional ligaments and the triangular fibrocartilage complex at the DRUJ.

Anatomy and joints: The PRUJ forms where the radial head articulates with the ulna’s radial notch, allowing rotation of the forearm. The DRUJ involves the ulnar head and the radius’s ulnar notch, also enabling rotation. The interosseous membrane runs obliquely between the radius and ulna, distributing load and maintaining relative alignment during forearm movement.

Movement and function: The radioulnar joints enable pronation and supination of the forearm. During rotation, the radius either crosses over the ulna or moves in parallel, depending on the direction. Typical ranges are roughly 75–90 degrees for pronation and 80–90 degrees for supination. Pronator muscles (such as pronator teres and pronator quadratus) drive pronation, while the biceps brachii and supinator drive supination.

Clinical relevance: Injuries include dislocations or fractures affecting either radioulnar joint. Monteggia fractures involve a proximal ulna fracture with radial head dislocation; Galeazzi fractures involve a distal radius fracture with DRUJ injury. Essex-Lopresti injuries combine a radial shaft fracture with interosseous membrane disruption and DRUJ instability. Chronic issues can include radioulnar synostosis or persistent instability.

Diagnosis and treatment: Evaluation uses forearm X-rays (AP and lateral) to assess alignment of the radioulnar joints and interosseous structures. Stable injuries may be managed with immobilization, while unstable or displaced injuries often require surgery (eg, ORIF, ligament or membrane reconstruction, DRUJ stabilization) and targeted rehabilitation to restore rotation and function.