Overview
The radius is the craniomedial bone of the forearm and carries most of the weight of the thoracic limb. It is shorter than the ulna, crosses slightly cranial to it and is joined to it by the interosseous ligament across a narrow interosseous space. In the dog, radius and ulna articulate at both ends and allow limited pronation and supination.
Key features
- Head (caput radii): proximal end with the fovea articulating with the capitulum of the humerus and the articular circumference articulating with the radial notch of the ulna.
- Radial tuberosity: medial, insertion of the biceps brachii and brachialis.
- Shaft: flattened craniocaudally, slightly curved.
- Trochlea of the radius (trochlea radii): distal end, concave articular surface for the radial carpal bone. It shows the ulnar notch laterally and the styloid process medially.
Clinical relevance
The distal radius is one of the most common sites of osteosarcoma in large-breed dogs. Radius and ulna fractures are among the most frequent in toy breeds (falls from the owner's arms), with a risk of non-union. Premature closure of the distal radial or ulnar physis causes angular limb deformities of the forearm and elbow incongruity.