It is a Sesamoid bone (bone embedded with a tendon) situated in the row of the Carpus (Cluster of bone in wrist between Radius and Ulna). The tendon that encapsulates this bone is called Flexor Carpi Ulnaris. Pisiform bone may be small but the joints it forms are very peculiar by nature. It makes a joint only with Triquetral. It is located where Ulna meets with Carpal bones.
Despite the other Carpal bone, Pisiform bone is not involved in the movement of wrist.
The fracture of Pisiform bone is most uncommon accounting 0.2% of all Carpal bone fractures. The treatment for it is to put a plaster cast or a wrist splint. The fracture can be easily missed on first presentation due to its laying position with other Carpal bones. MRI (Magnetic Resonance Imaging) is helpful in confirmation of diagnosis. If the early diagnosis is missed, it may result into Non Union. The treatment for Non Union is managed by surgical excision of Pisiform bone.