Metacarpophalangeal / Proximal & Distal Interphalangeal Joints (MCP / PIP / DIP)

The three joints from the base of a finger to its tip, standard vocabulary for describing dexterous-hand structure.

These three abbreviations come from human hand anatomy. MCP is the metacarpophalangeal joint, where the finger meets the palm; it can both flex/extend and move side to side, giving it 2 degrees of freedom. PIP is the middle joint, the proximal interphalangeal joint, and DIP is the joint nearest the fingertip, the distal interphalangeal joint; each of these can only flex and extend. When a person curls a finger, the DIP joint mostly follows the PIP joint's motion automatically, so many dexterous hands couple the two together with a linkage or tendon, letting one motor drive both joints — which means the hand ends up with more joints than actuated degrees of freedom (motors). The thumb's structure is different and has no separate PIP/DIP. When reading a dexterous hand's specs, distinguishing joint count from actuated degrees of freedom is necessary to compare products fairly.

ExampleEach finger on the Inspire RH56 dexterous hand has only one motor, which drives both the MCP and PIP joints to flex together through a linkage — so the whole hand has 12 joints but only 6 actuated degrees of freedom.

Also called

MCP Joint, PIP Joint, DIP Joint

Related

Dexterous Hand · Active DoF / Passive DoF · Thumb Opposition · Flexion/Extension and Abduction/Adduction · Underactuation · MANO

Sources

Metacarpophalangeal joint - Wikipedia
Interphalangeal joints of the hand - Wikipedia