Lunate

The lunate is one of the eight carpal bones in the human wrist. Its name comes from the Latin luna, meaning moon, reflecting its crescent shape. It occupies the center of the proximal row of carpal bones, lying between the scaphoid laterally and the triquetrum medially.

Anatomy and articulations: The lunate articulates proximally with the distal radius, forming part of the radiocarpal joint. Distally it interfaces with the capitate, and it also has contacts with the scaphoid laterally and the triquetrum medially. Its articulation pattern allows the wrist to flex, extend, and adapt to complex hand movements.

Clinical significance: The lunate is central to several wrist conditions. Lunate dislocation or fracture can follow a high‑energy hyperextension injury and may threaten the radiocarpal and midcarpal joints, often presenting with wrist swelling and pain. Kienbock disease refers to avascular necrosis of the lunate, a condition that can cause chronic wrist pain and limited motion and may arise from compromised blood supply to the bone. Proper assessment often relies on plain radiographs, with MRI or CT used to evaluate complications such as avascular necrosis or fracture displacement.

Diagnosis and treatment: Diagnosis typically involves imaging of the wrist, including X‑rays in multiple views; MRI is used to assess vascular status in suspected Kienbock disease. Treatment depends on the specific injury: stable fractures may be managed with immobilization, while dislocations or unstable fractures often require reduction and surgical repair or fixation. Management aims to restore joint stability and preserve wrist function, with prognosis varying by injury type and severity.