Underarmer

Underarmer, the Swedish term for the forearm, refers to the region of the upper limb between the elbow and the wrist. In humans, the forearm contains two long bones, the radius and ulna, linked by an interosseous membrane. These bones create two compartments: the anterior (flexor-pronator) compartment and the posterior (extensor-supinator) compartment, separated by intermuscular septa. The muscles of the anterior compartment primarily flex the wrist and fingers, while the posterior compartment contains muscles that extend and supinate the hand.

Movement is enabled by the radioulnar joints, with pronation and supination rotating the forearm around its longitudinal axis to change palm orientation. Nerves supporting the forearm include the median nerve, which supplies many anterior forearm muscles; the ulnar nerve, which supplies two of the anterior forearm muscles; and the radial nerve, which innervates the posterior compartment. The vascular supply comes from the radial and ulnar arteries, with venous drainage following corresponding pathways.

Clinical relevance includes fractures of the radius or ulna (often at the mid-shaft or near the joints), with variants such as Monteggia and Galeazzi injuries describing specific displacements. Compartment syndrome is a critical condition requiring urgent treatment to prevent muscle necrosis and nerve damage. Tendinopathies, such as lateral epicondylitis (tennis elbow), involve forearm extensor muscles. Anatomical variation exists among individuals, including accessory bones or differences in tendon attachments, reflecting natural variation in forearm anatomy.