The two sesamoids, embedded in the thick fibrous plantar plate and united to the proximal phalanx of the big toe, form an anatomic and functional unit called the sesamophalangeal apparatus (Fig. 16-11). The sesamoids are foci of insertion: the flexor hallucis brevis inserts on the proximal segment of each sesamoid, the lateral head of the flexor hallucis brevis and abductor hallucis inserts on the medial sesamoid, and the lateral sesamoid gives insertion to the oblique and transverse components of the adductor hallucis muscle. The deep transverse metatarsal ligament attaches longitudinally along the lateral sesamoid (Fig. 16-21). According to Sarrafian, the sesamophalangeal apparatus moves backward or forward relative to the fixed metatarsal head; in hallux valgus the sesamoids follow the proximal phalanx and are displaced with the phalanx, not with the metatarsal head.