Joint · Foot

First metatarsophalangeal joint

Articulatio metatarsophalangealis prima

The big toe joint, at the ball of the foot. The head of the first metatarsal meets the base of the big toe's first phalanx, and two small sesamoid bones sit underneath it, embedded in tendon and taking load directly. Every step you take finishes here: as the heel lifts, the body rolls over this joint and the toe must bend upward far enough to let you push off. If it cannot, the foot finds a way around it — and the compensation travels up the leg.