What Are the Symptoms of a Ulnar Shaft Fracture?

Fractures of the ulna shaft—the long, slender bone running along the medial side of the forearm—typically present with a constellation of clinical signs and symptoms that reflect both bony disruption and associated soft-tissue injury. Patients commonly report acute, localized pain over the middle to distal third of the forearm, often exacerbated by rotation (pronation or supination) or axial loading. Swelling and tenderness are nearly universal, frequently accompanied by visible deformity—such as angulation, shortening, or abnormal contour—especially in displaced or comminuted fractures. Ecchymosis may develop within hours to days, tracking distally toward the wrist or proximally toward the elbow.

Functional impairment is prominent: patients are typically unable to bear weight through the affected arm and experience significant weakness during grip or forearm rotation. In cases involving concomitant radius fracture—most notably in isolated ulnar shaft fractures resulting from direct trauma (e.g., “nightstick” injuries) or in Monteggia or Galeazzi patterns—clinical findings may extend beyond the ulna itself. Neurovascular assessment is critical; although the ulnar nerve lies adjacent to the distal medial humerus and does not course closely alongside the ulnar shaft, compromise of the posterior interosseous nerve (a branch of the radial nerve) or the anterior interosseous nerve (a branch of the median nerve) can occur due to swelling, hematoma, or direct contusion, manifesting as subtle motor deficits—such as weakened thumb IP joint flexion or index finger DIP flexion—without overt sensory changes.

Compartment syndrome remains a rare but limb-threatening complication, particularly in high-energy injuries or when swelling is disproportionately severe. Key warning signs include pain out of proportion to physical findings, pain with passive stretch of the fingers, palpable tenseness of the forearm compartments, and, in advanced cases, paresthesias or motor weakness. Prompt recognition and surgical consultation are essential to prevent irreversible muscle and nerve damage.