The pisohamate ligament connects the pisiform to the hamate hook, transmitting the force of the FCU through the pisiform to the hamate and fifth metacarpal (via the pisometacarpal ligament). These ligaments make the pisiform functionally equivalent to the patella — a sesamoid bone that redirects a tendon force through bony pulleys. Hook of hamate fractures can disrupt the pisohamate ligament, producing pisiform hypermobility and FCU biomechanical disruption.
| Origin | Pisiform bone |
|---|---|
| Insertion | Hook of the hamate |
| Actions | Transmits flexor carpi ulnaris tension to the hamate and fifth metacarpal via the pisometacarpal ligament — the pisiform is a sesamoid in the FCU tendon acting through these ligaments |
|---|
Pisohamate ligament disruption following hook of hamate fractures or pisotriquetral arthrosis produces ulnar wrist pain from the disrupted pisiform mechanics. Pisiform excision for pisotriquetral arthritis also divides the pisohamate ligament, which is acceptable because the FCU force is redirected to the pisohamate floor of Guyon canal.
Degenerative joint disease at the pisotriquetral articulation producing ulnar wrist pain on direct palpation, managed with corticosteroid injection and pisiform excision for refractory cases.
