Joint · Foot

Metatarsophalangeal joints (foot)

The row of joints across the ball of the foot, where each toe meets its long metatarsal bone. Structurally they are the toes' knuckles and are classed the same way as the hand's, with a rounded metatarsal head in a shallow socket permitting bending, straightening and a little side-to-side splay. What they do, though, is nothing like a knuckle's: at the end of every step the heel lifts, the toes bend upwards and the entire body weight crosses this row while the joints are in that extended position. The great toe's joint is the largest, carries two sesamoid bones in the tendon beneath it and takes the greatest share of that load — enough that it is described separately from the rest of the row.