alkarcsont

Alkarcsont is a term used in some languages to refer collectively to the forearm bones, the radius and the ulna. These two long bones extend from the elbow to the wrist and form the forearm’s central framework, enabling rotation and load transmission between the hand and the upper arm. They are connected by an interosseous membrane and by both proximal and distal radioulnar joints.

Anatomy and joints

The radius lies on the thumb side of the forearm and the ulna on the little finger side. At the elbow, the proximal radioulnar joint allows rotation of the forearm around the ulna, while the distal radioulnar joint provides a pivot near the wrist. The two bones interact with the humerus at the elbow and with the carpal bones at the wrist. The interosseous membrane binds the shafts of the radius and ulna, helping distribute loads.

Development and variation

Radius and ulna ossify from fetal cartilage models with growth plates at their ends, enabling postnatal lengthening until adolescence. Individual variations in length, curvature, and the relative sizes of the two bones are common and usually of no clinical consequence.

Function

The forearm bones enable pronation and supination, allowing the palm to face up or down. They transfer axial loads from the hand to the upper arm and provide attachment sites for forearm muscles that control wrist and finger movements.

Clinical significance

Fractures of the forearm—injuries to one or both of the radius and ulna—are common and include distal radius fractures, Monteggia and Galeazzi injuries. Nerve and vessel injuries can accompany forearm trauma, and distal radioulnar joint instability may complicate certain fractures.

See also: humerus, carpal bones, elbow joint.