Arm and hand skeleton (humerus, radius/ulna, hand)
Knowing the bones inside the arm and hand so you can place elbows, wrists, and fingers in believable positions from any angle.
What it is
You know the simple structure of the upper limb: one bone in the upper arm (humerus), two in the forearm (radius and ulna), and a block-and-fan of small bones in the wrist and hand. You can sketch that scaffold quickly, before adding muscles, skin, or clothing.
When you draw an arm, you place the humerus first — how it angles from the shoulder, where the elbow sits, and how thick that segment is. From elbow to wrist, the radius and ulna work as a pair that crosses and uncrosses for pronation and supination, turning the palm down or up. Knowing which bone sits on which side of the forearm affects the contour you draw.
For the hand, think of a solid wrist block leading into five rays: an angled thumb metacarpal and four finger metacarpals that fan out. You don't need every carpal bone memorized — just that the wrist has depth, the palm isn't flat, and each finger is a chain of three small bones hinged on that palm block.
On the job, this means you can invent or adjust arms and hands without perfect reference. You can rotate a forearm in your mind and keep the wrist aligned, change a hand pose and know where the knuckles move, and draw sleeves and gloves that wrap a solid structure instead of collapsing into noodles and mittens.
Why it matters
Without a clear mental skeleton, arms bend in the wrong place, elbows float, and forearms look like straight tubes that somehow twist 180° with no joint. Hands turn into flat paddles, finger joints stack wrong, and knuckles drift. Gesture suffers, and even well-painted characters feel off because you're fighting basic structure. Once the humerus, radius/ulna, and hand bones are clear in your mind, you can pose arms convincingly, keep volumes consistent, and support any level of rendering.
You can check it when
- ✓You can draw an arm from shoulder to fingertips as simple bones (humerus, radius/ulna pair, hand block and finger segments) from multiple angles without reference.
- ✓You can place the elbow and wrist in the right spots along the arm, and your drawn arms bend at those joints rather than in the middle of segments.
- ✓You can rotate a forearm (palm up, palm down, thumb up) and still keep the bony alignment of wrist, thumb base, and knuckles believable.
- ✓Your hands show clear structure: a wrist block with thickness, a palm that has length and arches, and fingers built from three small segments instead of sausages.