Injuries to the radioulnar joint in the forearm can range from ligament damage to dislocation or fracture. Symptoms include pain, swelling, and stiffness. Overuse can lead to ligament strains, while sudden force can cause dislocation or fracture. Two joints allow the forearm to rotate, and injuries often occur during rotational movements.
A radioulnar joint injury is an injury sustained to one of the two joints between the radius and ulnar bones in the human forearm, the proximal radioulnar joint below the elbow, or the distal radioulnar joint above the wrist. The types of injuries sustained can range from dislocated or broken bones in the joint to damage to the ligaments surrounding the joint. Symptoms of an injury to this area may include pain at the site and rotation of the forearm, swelling, tenderness, stiffness, and complete inability to move the injured joint.
At the proximal radioulnar joint, where the parallel radius and ulna meet at their highest points, the articular surfaces are the head of the radial bone along its medial or inner side and the radial notch of the ulna, a depression oblong near the top of the bone just below the elbow. This joint comprises a cylindrical bone – in this case the head of the radius – that rotates within a ring of ligament attached to the ulna known as the annular ligament. Like a ring on a finger, the annular ligament surrounds the head of the radius and allows it to rotate back and forth along the ulna.
At the inferior joint of the radius and ulna, the distal radioulnar joint, the adjacent surfaces are opposite those of the proximal joint: the cylindrical head of the ulna meets the ulnar notch at the bottom of the radius. In this case, the two are held together not by a ring-shaped ligament but by the volar and dorsal radioulnar ligaments, horizontal ligaments that connect the anterior and posterior aspects of the bones, respectively. This design allows the entire radius to rotate beyond the ulna during forearm rotation.
Since these two joints make it possible for the forearm to rotate, injuries of the radioulnar joint, especially ligament damage, can occur during rotational movements of the arm. Frequent and repetitive forearm rotation — both pronation, such as when turning the hand palm down, and supination, such as when turning the hand palm up — can lead to ligament strains or even gradual tears from overuse. This can be seen in athletes such as tennis players or workers whose job requires frequent forearm pronation and supination, such as in turning a dial. Symptoms of ligament damage in both joints will most likely include inflammatory pain, swelling, and stiffness with movement.
More serious injuries include dislocation, in which one or both bones separate from the joint, or fractures, in which one or both bones separate from the joint. These types of injuries are more likely to occur from an impact or other sudden force. An example can be seen at the distal joint, as in rotating the hand palm down to catch during a fall and dislocate or fracture one of the bones. Most commonly, the head of the ulna is damaged, an injury known as a dorsal subluxation. Symptoms of this injury include pain above the wrist, a prominent head of the ulna that protrudes from the little finger side of the arm, and the inability to supinate the forearm or raise the palm of the hand.
Another example of a radioulnar joint injury involving dislocation, this one seen at the proximal joint, is known as radial head subluxation or nurse’s elbow. Again, this is most often sustained when the forearm is pronated and involves dislocation of the radial head from the annular ligament which is often caused by a sharp jerk of the arm. This injury tends to be seen in young children, as well as by a stronger adult, and symptoms include pain that occurs low in the forearm away from the site of the injury, slight swelling, and an inability to supinate the forearm or turn the hand with the palm up .
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