Unterarms

Unterarms, or forearms in human anatomy, refer to the region of the upper limb between the elbow and the wrist. In humans they contain two long bones, the radius and the ulna, connected along their length by an interosseous membrane. The proximal and distal radioulnar joints permit rotation of the forearm, enabling pronation and supination. The radiocarpal joint links the forearm to the wrist.

Anatomy and compartments: The forearm houses muscles organized into an anterior (flexor) compartment and a posterior (extensor) compartment. Flexors originate mainly from the medial side of the elbow; extensors from the lateral side. Key muscles include pronator teres, flexor digitorum superficialis and profundus, and flexor pollicis longus in the anterior compartment; extensor carpi radialis longus and brevis, extensor digitorum, extensor carpi ulnaris, and supinator in the posterior compartment.

Vessels and nerves: The brachial artery gives rise to the radial and ulnar arteries. The median nerve supplies most of the anterior forearm; the ulnar nerve supplies the medial forearm; the radial nerve supplies the posterior compartment. The interosseous membrane provides additional stability between the two bones.

Function: The forearm enables rotation (pronation and supination), flexion and extension at the wrist, finger movements, and the transmission of forces from hand to upper arm. It also serves as a lever system for grip and manipulation of objects.

Clinical relevance: Common injuries include fractures of the radius and/or ulna, with patterns such as Monteggia and Galeazzi fractures. Overuse injuries can affect forearm tendons and nerves, and distal radius fractures are frequent after falls.