Each human hand contains 27 bones, divided into three main groups: the carpals (wrist bones), the metacarpals (palm bones), and the phalanges (finger bones). A few small sesamoid bones embedded in tendons bring the total slightly higher, though they’re not always counted in the standard 27.
The Three Groups of Hand Bones
Your hand’s 27 bones work together as a system. Eight small carpal bones form the wrist. Five metacarpal bones span the palm. And 14 phalanges make up your fingers and thumb. Each group has a distinct shape and role, and together they give the hand its remarkable combination of strength and precision.
Carpal Bones: The Eight Wrist Bones
The eight carpal bones are arranged in two rows of four, stacked between your forearm and your palm. They’re small, irregularly shaped, and fit together like cobblestones.
The proximal row (closer to the forearm, moving from thumb side to pinky side):
- Scaphoid, the most commonly fractured carpal bone, accounting for about 60% of all wrist bone fractures
- Lunate, which sits in the center of the wrist
- Triquetrum, on the pinky side
- Pisiform, a small pea-shaped bone that sits on top of the triquetrum
The distal row (closer to the fingers, again from thumb side to pinky side):
- Trapezium, which connects to the thumb’s metacarpal and allows the thumb’s wide range of motion
- Trapezoid, the smallest bone in the distal row
- Capitate, the largest carpal bone, sitting in the center
- Hamate, recognizable by a hook-shaped projection on its palm side
Babies aren’t born with fully hardened carpal bones. Instead, these bones start as cartilage and gradually ossify over childhood. The capitate and hamate harden first, typically by six to eight months of age. The pisiform is the last to fully ossify, sometimes not completing until age 10 in girls or as late as 14 in boys. This predictable timeline is why doctors sometimes use a hand X-ray to assess a child’s skeletal maturity.
Metacarpals: The Five Palm Bones
The metacarpals are the five long bones that fan out across your palm, connecting the wrist to the fingers. They’re numbered 1 through 5 starting from the thumb side. You can feel their tops (the “heads”) as the knuckles at the base of your fingers when you make a fist.
The first metacarpal, at the base of the thumb, is shorter and more mobile than the others. The second and third metacarpals are relatively rigid, giving the hand a stable central column for gripping. The fourth and fifth metacarpals have more flexibility, which is why the pinky side of your hand can cup inward to wrap around objects of different shapes and sizes. A fracture of the fifth metacarpal neck, sometimes called a boxer’s fracture, is one of the most common hand injuries.
Phalanges: The 14 Finger Bones
Each finger has three phalanges, and the thumb has two, for a total of 14. They’re named by position:
- Proximal phalanx, the bone closest to the palm
- Middle phalanx, the bone in the center of each finger (the thumb doesn’t have one)
- Distal phalanx, the bone at the fingertip, just below the nail
The thumb’s lack of a middle phalanx isn’t a limitation. Having only two bones actually gives the thumb a different mechanical advantage, allowing it to oppose the other fingers for pinching and gripping.
Sesamoid Bones
Beyond the standard 27, most people have about five sesamoid bones in each hand. These are tiny, seed-shaped bones embedded within tendons rather than connected directly to other bones. Two sit at the base of the thumb, one at the thumb’s fingertip joint, and the remaining two are found near the base of the index finger and pinky finger. Their job is to reduce friction and redistribute force through the tendons, protecting them from strain during gripping and pinching.
How the Joints Connect Them
The bones of the hand meet at four types of joints, each allowing a different degree of movement.
The carpometacarpal (CMC) joints connect the wrist bones to the palm bones. The thumb’s CMC joint is the most mobile of the group, allowing the thumb to bend, extend, rotate, and move toward and away from the hand. The index and middle finger CMC joints are nearly rigid, providing stability. The ring and pinky CMC joints are more flexible, letting the hand reshape itself to grip objects of varying sizes.
The metacarpophalangeal (MCP) joints are your main knuckles, where the palm bones meet the finger bones. These joints let you bend your fingers toward your palm, extend them straight, and spread them apart or bring them together. They’re essential for both power grip and fine pinch.
The proximal interphalangeal (PIP) joints are the middle knuckles of your fingers. They work like hinges, allowing each finger to bend and straighten but not move side to side. The distal interphalangeal (DIP) joints, located just below the fingernails, work the same way but with a smaller range of motion. The thumb has only one interphalangeal joint, since it lacks a middle phalanx.
Why the Scaphoid Matters Most in Injuries
Of all the hand and wrist bones, the scaphoid deserves special mention because it fractures far more often than any other carpal bone. It breaks most commonly when you fall onto an outstretched hand. The tricky part is that scaphoid fractures sometimes feel like a mild wrist sprain, with tenderness concentrated in the small depression at the base of the thumb (called the “anatomical snuffbox”). Because the scaphoid has a limited blood supply, fractures that go undiagnosed and untreated can lead to the bone losing blood flow and deteriorating over time. If you have persistent pain in that area after a fall, an X-ray or follow-up imaging can catch what an initial exam might miss.