Pisiform bone joint, articulating with the triquetral bone. It is on a plane anterior to the other carpal bones and is spheroidal in form. The pisiform bone has four surfaces: Unlike the other carpal bones, the pisiform is not involved in movement of the wrist. The etymology derives from the Latin "pīsum" which means "pea". All other tetrapods have pisiform, being the most common sesamoid. As compared with apes, which have an elongated Pisiform, humans have a shorter pisiform bone. This is due to the loss of the single growth plate typically found in other mammalian pisiforms. This may be because of
Limbs of the horse the pisiform is the back of the knee. Below the knee is the cannon bone which is also known as the 3rd metacarpal. 55 million years ago when the Eohippus existed, the cannon bone used to be the 3rd toe of the foot. Its fusion took place in order to increase height and power of the limb. Behind the cannon bone are the splint bones. The splint bones are also known as the 2nd and 4th metacarpal and fused 25 - 35 million years ago during the time of the Miohippus. They provide extra strength and support of the cannon