A finger does not have 3 knuckles. The term “knuckle” is commonly used to refer to the metacarpophalangeal joint, or MCP joint, which is located at the base of each finger or thumb. This joint connects the metacarpal bone to the proximal phalanx bone of each finger.
Each finger actually has three separate joints, not including the MCP joint. These joints are known as the interphalangeal joints. The fingers, excluding the thumb, have three phalanges: the proximal phalanx, the middle phalanx, and the distal phalanx. The proximal phalanx is connected to the metacarpal bone at the MCP joint, while the middle and distal phalanges are connected by the interphalangeal joints.
In total, each finger has two interphalangeal joints, one between the proximal and middle phalanges, and another between the middle and distal phalanges. The thumb, on the other hand, only has one interphalangeal joint. Therefore, a finger has a total of four joints: one MCP joint and three interphalangeal joints.
To provide a clearer understanding, let’s break it down by finger:
1. Thumb:
– MCP joint: connects the metacarpal bone to the proximal phalanx.
– Interphalangeal joint: connects the proximal phalanx to the distal phalanx.
2. Index finger, middle finger, ring finger, and little finger:
– MCP joint: connects the metacarpal bone to the proximal phalanx.
– Interphalangeal joint 1: connects the proximal phalanx to the middle phalanx.
– Interphalangeal joint 2: connects the middle phalanx to the distal phalanx.
So, while the MCP joint is commonly referred to as the knuckle joint, a finger actually has multiple joints, including the MCP joint and two interphalangeal joints.