1 The first and largest knuckle is the junction between the hand and the fingers-the metacarpophalangeal joint (MCP). 2  This joint commonly is injured in closed-fist activities and is commonly known as a boxer's fracture. 3  The next knuckle out toward the fingernail is the proximal inter-phalangeal joint (PIP).he three bones in each finger are named according to their relationship to the palm of the hand. The first bone, closest to the palm, is the proximal phalange; the second bone is the middle phalange; and the smallest and farthest from the hand is the distal phalange.