The joint between the big toe (proximal phalange) and the foot (metatarsal bone) is called 1st metatarsal-phalangeal joint (1st MTPJ). The head of the 1st metatarsal bone is twice the size of the 2nd metatarsal so that it is a major weight bearing area of the foot. There are two small sesamoid bones help the weight bearing and act as pulley systems to increase the mechanical advantage of the plantar muscles. The 1st MTPJ is not a simple hinge joint. The metatarsal has to slide downward before the big toe can bend upward because of the structure of the articular surface.