radioulnar

Radioulnar refers to structures involving the radius and ulna, the two long bones of the forearm. They connect at the elbow and the wrist through a pair of joints known as the proximal and distal radioulnar joints. An interosseous membrane runs along the length of the two bones, binding them together and facilitating load transfer as the hand and forearm move.

The proximal radioulnar joint is formed by the radial head articulating with the radial notch of the ulna. It is stabilized by the annular ligament, which encircles the radial head. The distal radioulnar joint is formed by the articulation between the ulna’s distal head and the ulnar notch of the radius, with stability provided largely by the triangular fibrocartilage complex (TFCC) and surrounding ligaments. The interosseous membrane between the radius and ulna also contributes to joint stability and force transmission.

Movement at the radioulnar joints enables forearm rotation, specifically pronation (turning the palm downward) and supination (turning the palm upward). These actions are produced primarily by the muscles of the forearm, including the supinator and the pronator teres (with assistance from the pronator quadratus), and are supported by the interosseous membrane. Nerve supply to these muscles is via the median nerve (for most anterior forearm muscles) and the deep branch of the radial nerve (for the supinator).

Clinically, radioulnar injuries are central to several forearm fracture patterns. Monteggia fractures involve a fracture of the proximal ulna with dislocation of the radial head at the proximal radioulnar joint, while Galeazzi fractures involve a distal radius fracture with dislocation of the distal radioulnar joint. Recognition of radioulnar joint integrity is important for proper forearm function and load transmission.