The distal radio-ulnar joint (DRUJ) is a pivotal joint located at the wrist, where the two forearm bones, the radius and the ulna, meet. It plays a vital role in forearm movements, specifically in pronation and supination, allowing our palms to turn upwards (as in holding a bowl of soup) or downwards.
Location
The Distal radio-ulnar joint is found at the distal end of the forearm, adjacent to the wrist. It is constituted by the articulation between the ulnar head and the ulnar notch of the distal radius.
Structure
- Joint Type: The Distal radio-ulnar joint is a pivot-type synovial joint. This means it allows for rotational movement around a central axis.
- Articular Surface: The ulnar head articulates with the ulnar notch of the radius, forming the joint.
- Ligamentous Support: The joint is stabilized by the dorsal and palmar radio-ulnar ligaments, which are essentially thickenings of the joint capsule and ensure stability during rotational movements.
- Triangular Fibrocartilage Complex (TFCC): This is a crucial structure that stabilizes the Distal radio-ulnar joint and also acts as a cushion between the ulna and the carpal bones of the wrist.
Function
- Forearm Rotation: The primary function of the DRUJ is to allow pronation and supination of the forearm. This rotational movement lets us use our hands in versatile ways, from turning a doorknob to using a screwdriver.
- Stability: While the DRUJ facilitates movement, it also provides stability to the wrist, ensuring the coordinated motion of the radius and ulna.
- Load Transmission: Through the TFCC, the DRUJ also participates in transmitting axial loads from the carpus to the ulna and vice versa.
Clinical Significance
Injuries
- DRUJ Dislocation: Trauma or forceful impacts can cause the head of the ulna to dislocate from its position. This is often painful and restricts wrist movement.
- TFCC Tears: These can result from traumatic injuries or degenerative changes. Symptoms include pain on the ulnar side of the wrist, especially during rotational movements.
Diagnostic Modalities
- Physical Examination: Tenderness over the DRUJ, swelling, and restricted movement are clinical signs of potential DRUJ problems.
- Imaging: X-rays can identify dislocations or fractures, while MRI is more sensitive for detecting TFCC tears or other soft tissue injuries.
Treatment
- Conservative: Mild injuries might be managed with rest, immobilization, and physical therapy.
- Surgical: Severe dislocations, TFCC tears, or chronic instability might necessitate surgical intervention.
