Thumb / Finger / Hand
Your thumb is very different from your other four fingers. To begin with, the thumb only has two bones (or phalanges) while the other fingers have three. The thumb is also opposable, meaning its enhanced freedom of movement enables you to touch your thumb to the tips of your other four fingers, allowing you to grasp objects. A system of muscles makes all this movement possible, and repeated use of these muscles puts stress primarily on two joints – the Basal joint, located at the very base of the hand between the thumb and the wrist, and the Metacarpophalangeal (MCP) joint, located at the base of the thumb.