Radius and Ulna
Radius et Ulna
Overview
The radius and ulna form the forearm (antebrachium), the segment between the elbow and the carpus. In the horse these two bones are fused, restricting movement to the sagittal plane with virtually no pronation or supination. The radius is the primary weight-bearing bone and carries the load from the elbow down to the carpus. The ulna contributes the olecranon tuberosity (point of the elbow), which provides leverage for the triceps muscle to extend the elbow, and then tapers distally, fusing with the radius at about mid-antebrachium. A small interosseous space remains in the proximal third and allows passage of blood vessels. The distal radius features medial and lateral styloid processes that articulate with the carpal bones.
Anatomical Details
Origin: N/A (bone)
Insertion: N/A (bone)
Action: Bears body weight between the elbow and carpus; the olecranon provides leverage for the triceps muscle to extend the elbow. The forearm is built to swing forward and back in one plane and carry weight efficiently, not to rotate.
Clinical Significance
Fractures of the radius are serious injuries that often require surgical repair and carry a guarded prognosis depending on configuration and soft-tissue damage. The olecranon can also fracture, affecting triceps function and elbow extension. Because the bones are fused, the forearm has no rotational capacity, which influences both normal biomechanics and injury patterns.
Common Conditions & Injuries
Radial fracture
## Overview Radial fracture is a break of the main forearm bone. In adult horses it is often catastrophic, resulting from kicks, falls, or racing injuries. Complete fractures cause non-weight-bearing
Olecranon fracture
## Overview Olecranon fracture is a break of the point of the elbow, usually from direct trauma such as a kick or fall. Because the triceps inserts on the olecranon, the horse cannot extend the elbow
What Horse Owners Should Know
Severe lameness with swelling of the forearm or inability to bear weight after trauma needs immediate veterinary attention. Do not attempt to walk the horse long distances until evaluated.
Frequently Asked Questions
What is Radial fracture in horses?
## Overview Radial fracture is a break of the main forearm bone. In adult horses it is often catastrophic, resulting from kicks, falls, or racing injuries. Complete fractures cause non-weight-bearing lameness, swelling, deformity, and crepitus. Open fractures are common. Prognosis in adults is extremely poor. ## Causes Trauma or propagation of a stress fracture. ## Diagnosis Clinical signs and radiographs. ## Treatment Internal fixation is rarely successful in adults because of bone size and opposite-limb complications. Most adult horses are euthanized. Foals have a better chance with surgery in selected cases. ## Recovery and Prognosis Grave in adults. Guarded in foals. ## Prevention Monitoring for stress fractures in racehorses. Signs include: acute severe non-weight-bearing forelimb lameness; swelling and deformity of the forearm; crepitus; may be open
What is Olecranon fracture in horses?
## Overview Olecranon fracture is a break of the point of the elbow, usually from direct trauma such as a kick or fall. Because the triceps inserts on the olecranon, the horse cannot extend the elbow and presents with a dropped elbow and non-weight-bearing lameness. Surgical repair with plates and screws is the treatment of choice for most displaced fractures and carries a generally good prognosis. ## Causes Direct trauma. In foals, excessive pull from the triceps can also cause fracture. ## Diagnosis Characteristic posture and radiographs of the elbow. ## Treatment Tension-band plating for displaced fractures. Some non-displaced fractures in foals may be managed conservatively. Prognosis is good with internal fixation. ## Recovery and Prognosis Good with appropriate surgical repair. ## Prevention Trauma avoidance. Signs include: dropped elbow; inability to bear weight; swelling at the point of the elbow; cannot extend the elbow
What are the clinical concerns for the Radius and Ulna?
Fractures of the radius are serious injuries that often require surgical repair and carry a guarded prognosis depending on configuration and soft-tissue damage. The olecranon can also fracture, affecting triceps function and elbow extension. Because the bones are fused, the forearm has no rotational capacity, which influences both normal biomechanics and injury patterns.
What should horse owners know about the Radius and Ulna?
Severe lameness with swelling of the forearm or inability to bear weight after trauma needs immediate veterinary attention. Do not attempt to walk the horse long distances until evaluated.
Explore This Structure in 3D
See the Radius and Ulna on our interactive 3D horse model. Open 3D Model