Background: Spontaneous flexor tendon rupture is rare and most common in the little finger. The pathogenesis of spontaneous tendon ruptures is unclear but may occur through attrition or mechanical abrasion over a bony prominence. Kienböck disease is avascular necrosis of the lunate, with an unknown etiology. Methods: We present a case of spontaneous rupture of flexor digitorum profundus due to Kienböck disease, which we believe is the first recorded case of flexor tendon rupture attributable to osteonecrosis of the lunate. Results: The patient underwent single-stage reconstruction of FDP and regained a good range of motion at the affected DIPJ. Conclusions: This case illustrates the the importance of plain radiographs in the assessment of a patient presenting with spontaneous flexor tendon rupture in the hand to exclude bony pathology as a cause.
