The ulnar styloid process and the triangular bone are relatively far away from each other, so when the trauma force is small, the two are not easily impacted or the impact force is small, which does not cause damage to the triangular bone or the bone marrow changes are slight, so the incidence of the triangular bone is low. When the strength of trauma and wrist retraction is large (especially the positive ulnar variation is greater than 2mm), the ulnar head and ulnar styloid process impact with the lunar bone and the triangular bone and form a bridging state, resulting in continuous compression, which will cause limited necrosis of the lunar bone and the triangular bone at the same time. Etiology 1.positive ulnar bone sign: the relationship between the distal ulnar articular surface and the radial sigmoid notch, if more than the positive ulnar bone sign, equal to the suspicious positive, shorter than the negative, is one of the most important factors in the formation of the disease. 2.The development of triangular fibrocartilage plate is weak, and the impact of the distal ulna on the lunar bone and triangular bone is more direct. 3.Denaturation of the triangular cartilage plate. 4.Chronic strain and long-term impingement. Clinical diagnostic criteria (1) history of wrist trauma or special hand work; (2) pain on the ulnar side of the wrist when the wrist is rotated or ulnar deviated or stressed, restricted wrist movement, positive ulnar tension test; (3) popping and pressure pain in the distal ulnar flexor joint area, especially the dorsal and lateral side of the ulnar carpal joint gap; (4) most of the wrist radiographs show ulna growing more than 2mm relative to the flexor bone (5) MRI of the wrist On examination, most of them show signal changes of the lunate bone and triangular bone, and some of them show signal changes of the triangular fibrocartilage.