Ulna - The medial bone of forearm

Ulna is the medial bone of the forearm on the side of the little finger and is longer than the radius. Side identification is done by keeping the olecranon process superiorly, the trochlear notch facing anteriorly, and the styloid process directed medially, Sharp interosseous border should face lateral. The ulna forms joints with the humerus at the elbow joint and with the radius at the superior and inferior radioulnar joints. The ulna does not directly participate in the wrist joint because it is separated from the carpal bones by an articular disc. Important muscle attachments include triceps brachii to the olecranon and brachialis to the coronoid process and ulnar tuberosity. Other muscles attached to the ulna are flexor digitorum profundus, pronator quadratus, supinator, abductor pollicis longus, and extensor pollicis longus. A night-stick fracture is an isolated fracture of the shaft of the ulna, usually caused by a direct blow when a person raises the forearm to protect the head. It is commonly seen in assault injuries and may present with pain, swelling, tenderness, and deformity along the subcutaneous border of the ulna.