Sesamoid bones of foot

The sesamoid bones of the foot are most consistently found beneath the head of the first metatarsal, at the plantar aspect of the first metatarsophalangeal (MTP) joint. There are typically two: the medial (tibial) sesamoid and the lateral (fibular) sesamoid. These bones are embedded within the tendons of the flexor hallucis brevis muscle and are connected by the intersesamoid ligament and the plantar plate, forming the hallux sesamoid complex. Their primary function is to act as a fulcrum, increasing the mechanical efficiency of the flexor tendons, absorbing weight-bearing stress, and protecting the tendons from friction and trauma.

Additional sesamoid bones may be present at other metatarsophalangeal joints, most commonly at the fifth MTP joint, and less frequently at the second, third, and fourth MTP joints. The prevalence of these varies by population, with the first MTP sesamoids present in nearly all individuals, while others are much less common.

An interphalangeal sesamoid may also be found beneath the hallux interphalangeal joint in a minority of cases.