Interphalangeal joints of foot Interphalangeal joints of foot The interphalangeal joints of the foot are between the phalanges (bones) of the toes. Since the great toe only has two phalanx bones (proximal and distal phalanges), it only has one interphalangeal joint, which is often abbreviated as the "IP joint." The rest of the toes each have three phalanx bones (proximal, middle, and distal phalanges), so they have two interphalangeal joints: the proximal interphalangeal joint between the proximal and middle phalanges (abbreviated "PIP joint") and the distal interphalangeal joint between the middle and distal phalanges (abbreviated "DIP joint"). All interphalangeal joints are ginglymoid (hinge) joints,
Phalanx bone terminal phalanges and fused metacarpal bones able to absorb the stress from running. The sloth spends its life hanging upside-down from branches, and has highly specialized third and fourth digits for the purpose. They have short and squat proximal phalanges with much longer terminal phalanges. They have vestigial second and fifth metacarpals, and their palm extends to the distal interphalangeal joints. The arboreal specialization of these terminal phalanges makes it impossible for the sloth to walk on the ground where the animal has to drag its body with its claws. Phalanx bone The phalanges (singular: "phalanx" ) are digital bones