The number of knuckles you have depends on how the term is defined. While common usage often points to the prominent joints at the base of the fingers, a more precise anatomical understanding reveals a greater number of these structures. These joints collectively enable the hand’s remarkable ability to perform a wide array of movements, from powerful grasps to delicate manipulations.
Understanding What a Knuckle Is
The term “knuckle” is used in everyday language to describe the visible joints of the fingers, particularly those that become prominent when a fist is made. Anatomically, however, a knuckle refers to any joint between the bones of the fingers. There are three main types of joints found in each of the four fingers (index, middle, ring, and pinky), and two in the thumb.
The first type, the metacarpophalangeal (MCP) joints, are located where the fingers meet the palm. These are the “main knuckles” that are most noticeable when clenching a fist. The proximal interphalangeal (PIP) joints are the middle joints of the fingers, situated between the first and second bones of each finger. The distal interphalangeal (DIP) joints are the joints closest to the fingertips. The thumb is unique, as it only has two bones (phalanges) and therefore only two joints: a metacarpophalangeal (MCP) joint and a single interphalangeal (IP) joint, which is comparable to a DIP joint in the other fingers.
Counting Your Knuckles
To accurately count your knuckles, it is helpful to consider the anatomical definition of each joint. Each of your four fingers (index, middle, ring, and pinky) contains three distinct joints: the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints. Therefore, each of these four fingers has three knuckles.
The thumb has a slightly different structure, composed of two bones and two joints: a metacarpophalangeal (MCP) joint and a single interphalangeal (IP) joint. This means the thumb contributes two knuckles to the total count.
Calculating the total number of knuckles per hand involves summing these joints. For the four fingers, each having three joints, this totals 12 joints (4 fingers 3 joints/finger). Adding the two joints of the thumb brings the count to 14 joints per hand (12 + 2). Therefore, a person typically has 28 knuckles in total across both hands (14 joints/hand 2 hands).
The Purpose of Knuckles
The joints in our fingers, commonly referred to as knuckles, are fundamental to the hand’s remarkable dexterity and range of motion. These joints, including the MCP, PIP, and DIP joints, allow for movements such as flexion (bending) and extension (straightening), which are necessary for daily activities. The MCP joints, for instance, enable the fingers to spread apart and come together, as well as bend and extend.
These articulations are supported by a complex network of soft tissues. Cartilage, a smooth and flexible connective tissue, covers the ends of the bones within each joint, allowing them to glide past each other with minimal friction. This cushioning effect absorbs shock and helps maintain smooth, painless movement. Ligaments, which are tough bands of fibrous tissue, connect bones to other bones, providing stability to the joints and preventing excessive or abnormal sideways movement.
Tendons, another type of fibrous tissue, connect muscles to bones, transmitting the force generated by muscles to move the joints. The coordinated action of these structures allows the hand to perform intricate tasks, from grasping large objects with a power grip to manipulating small items with a precision grip. This integrated system of bones, cartilage, ligaments, and tendons ensures the hand can adapt to various shapes and sizes, underscoring the functional importance of each knuckle.