The first knuckle is the metacarpophalangeal joint (MCP), located at the base of the finger where the hand bone meets the finger bone. It's the largest knuckle and is often the one that gets injured in closed-hand punches.
The metacarpophalangeal joint (MCP) is the joint between the metacarpal bone (in the hand) and the first phalanx (in the finger). This joint allows for bending and straightening of the finger.
While the knuckles at the base of the fingers (MCP joints) are often called the "first knuckles," it's important to note that some sources might use the term "first knuckle" to refer to the proximal interphalangeal joint (PIP), which is the joint between the first and second phalanx of the finger.
For clarity, it's best to specify whether you're referring to the MCP joint (the knuckle at the base of the finger) or the PIP joint (the knuckle in the middle of the finger) when talking about the "first knuckle."
