The triquetrum refers to a part of the wrist known as the triquetral bone. Specifically, the bone is part of the carpus, a group of eight wrist bones. The triquetrum and other bones in the carpus are located between the two major bones in the forearm, the radius and ulna. The triquetral bone is situated between two carpal bones known as the lunate and pisiform. It is partly covered by the pisiform bone. The triquetrum is found right above the end of the ulna bone. Its functional ability is not dependent on the ulna bone. It acts in tandem with the pisiform carpal bone and the ulnar collateral ligament. The triquetrum is pyramidal in shape, with five different sections designated on three distinct sides of the bone. The triquetral bone is the third most common site of carpal bone fractures. Triquetrum fractures are especially common amongst those who play sports. Fractures generally occur when the wrist is overextended. A small portion of the bone may be chipped off, or the fracture can run through the middle of the bone.