A clicking finger. A burning wrist. An elbow that aches after a full day of typing. Each of these points at a specific structure doing a specific job under strain, and once you can picture that structure, your own pain gets a lot less mysterious. That’s what this section is for. Plain-language anatomy of the finger, hand, wrist, forearm and elbow, region by region, with the problems each structure tends to cause. Read the part that hurts, and the condition articles on this site will make twice as much sense.
Fingers and thumb
Each finger has three bones called phalanges, stacked end to end, and three joints: the knuckle where the finger meets the hand, the middle joint, and the small joint near the tip. The thumb runs on two bones instead of three, but makes up for it at its base, where a saddle-shaped joint lets it swing across the palm to meet the other fingertips. That one movement, opposition, is most of what makes a human hand a human hand. It’s also why thumb problems cost you more function than any single finger.
Here’s the part that surprises most of my patients: there are no muscles in your fingers. None. Everything that moves them gets pulled from the palm and forearm through tendons, a bit like a puppet. On the palm side, two flexor tendons per finger run through a tunnel of pulleys, small fibrous straps that hold the tendons tight against the bone so they don’t bowstring away when you grip. On the back, a flat extensor system straightens the finger and splits into fine bands near the tip.
Once you know that layout, finger problems sort themselves. Trigger finger is the flexor tendon catching on the first pulley at the base of the finger. A climber’s pop on a crimp is one of those pulleys tearing. Mallet finger is the thin extensor band at the tip giving way, so the fingertip droops. Same machine, different broken part.
Hand and palm
Five long bones, the metacarpals, form the body of the hand, and unlike the fingers, the hand does have muscles of its own. The fleshy pad below your thumb and the smaller one below your little finger are muscle groups that position those digits. Between the metacarpals sit small muscles that spread your fingers, pull them together, and fine-tune your grip. When surgeons and therapists worry about a nerve injury, part of what we’re watching is whether these small muscles are wasting, because they’re the difference between a hand that holds and a hand that handles.
The palm also explains why some fractures matter more than their size. The ring and little finger side of the hand is built to fold and grip around objects, so a break there that heals with the finger slightly rotated will make that finger cross over its neighbour in a fist. Millimetres of rotation at the bone become centimetres of overlap at the fingertip.
Wrist
Eight small carpal bones packed into two rows, tied together by more ligaments per square centimetre than nearly anywhere else in your body. The wrist gives up stability to buy you mobility. A fair trade, until the day you fall on it.
Two structures here earn their own mention. First, the scaphoid, the boat-shaped bone at the base of the thumb, which receives its blood supply backwards, entering at the far end and flowing towards the near end. Break it in the middle and the near half can slowly starve. That quirk of plumbing is why a “wrist sprain” after a fall, with tenderness in the hollow at the thumb’s base, gets treated with so much suspicion. Second, the carpal tunnel, a rigid passage on the palm side roughly the width of your thumb, carrying nine flexor tendons and the median nerve. Nine tendons and a nerve in one small tunnel: any swelling in there has nowhere to go except into the nerve, and you feel it as night-time tingling in the thumb, index and middle fingers.
On the little-finger side sits the TFCC, a cartilage complex that cushions and stabilises where the forearm meets the wrist. It loads every time you rotate the forearm or push through your hand, which is why a torn one complains when you press up from a chair.
Forearm
Two bones, radius and ulna, rotating around each other every time you turn a key or a doorknob. Palm up, they lie parallel. Palm down, the radius has crossed over the ulna. That rotation, pronation and supination, is a movement people don’t think about until it hurts, and then they discover it’s in everything: pouring, typing, turning taps, using a screwdriver.
Nearly all the muscles that power your grip and move your wrist and fingers start here. The muscles that close your hand arise mostly from the inner elbow; the ones that open the hand and cock the wrist back arise from the outer elbow. So the forearm is where the horsepower lives, and the hand is mostly cables and levers. In clinic, patients point at where it hurts, usually the wrist or the elbow. The problem often lives one joint away, in the forearm doing the actual work.
Elbow
Three bones meeting in one capsule, doing two jobs at once: a hinge that bends and straightens the arm, and a pivot that lets the forearm rotate. The bony point on the outer side anchors the wrist and finger extensor muscles, and overload there is tennis elbow. The inner point anchors the flexors, and that’s golfer’s elbow. Neither needs the sport; both need grip, which is why a week of heavy lifting, gardening or carrying a new baby can light them up.
Behind the inner elbow, the ulnar nerve runs exposed in a shallow groove, which is exactly the zing you feel when you knock your funny bone. Because it sits so close to the surface and stretches every time the elbow bends, it’s also the nerve that complains after long evenings with the elbow folded, phone in hand or head propped up, felt as tingling in the ring and little fingers.
The three nerves, and how to read their signals
Three nerves run the whole show, and each owns its own territory of skin. That’s clinically useful, because where you feel tingling tells us which nerve is unhappy, and roughly where.
The median nerve feels the thumb, index, middle and half the ring finger on the palm side, and it’s the one squeezed in carpal tunnel syndrome. The ulnar nerve feels the little finger and the other half of the ring finger, and runs most of the hand’s small muscles; it gets irritated at the inner elbow. The radial nerve mostly powers the muscles that lift the wrist and fingers, and feels the back of the hand near the thumb. Tingling in thumb-index-middle points to the wrist. Tingling in ring-and-little points to the elbow. Different postcode, different nerve, different problem.
Why anatomy comes first
Every condition article on this site names the structures involved. Once you can picture the tendon catching on its pulley, or the nerve squeezed in its tunnel, treatment stops being mysterious. You understand why a splint holds one joint still and leaves the next one free, why a tendon needs loading rather than pure rest, and why week 2 of your recovery runs on different rules from week 6.
My patients who understand their own anatomy recover better. Not because knowing is magic. Because they stop doing the things that were quietly making it worse.
Written by Nigel Chua, hand occupational therapist in practice since 2005. My credentials are here.