I’m rereading “The Chamber of Secrets” and just got to the part where Prof. Lockhart inadvertently removes Harry’s arm bones. Thankfully the infirmary is equipped with Skele-gro, but it’s mentioned that Harry has to regrow 33 bones. So there’s 27 bones in the hand and wrist, plus the radius, ulna, and humerus. That leaves the total three short. What’s missing?
A wizard did it.
I am thinking it is just an error.
I’ll go with Mahaloth here it is probably just an editing error no one caught.
But you did so Congrats! you get a gold star.
If you throw in the shoulder, you could add the scapula and clavicle, but that would only get you to 32. Maybe male wizards have an extra bone or three in their hands to improve their–ahem–wand manipulation.
But yes, it’s just a mistake, either in the research or in the writing.
Cool! It’s been a long time since I got one. Where do I pick it up?
On the other hand, Harry’s in an infirmary, not a hospital. My friend once went to the college infirmary with a sore wrist, the day after an ill-advised attempt to recreate “The Fly” move from The Karate Kid after a few too many Lucky Lagers. He asked if it was broken, and the nurse told him, “The only way I’d know it was broke is if it fell off.” I don’t believe he quizzed her on the total count of bones in his hand, but I’m skeptical she’d have gotten it right.
Children do have more bones than adults, although I don’t know exactly when they “lose” some (or rather, bones fuse together). Infants are born with around 300 “bones”*, and adults generally have 206. Maybe Harry still had a few baby wrist bones in there at the age of, what, 10?
*Some of these being cartilaginous, rather than bone tissue, but that’s a nit I’d rather not pick.
You know, that’s sort of brilliant. The long bones in a 12 year-old would have epiphyseal plates, which in a sense divide the bone into two. That brings the total right to 33. However, I think there would be epiphyseal plates on each end of the bone, which brings the total to 36. Oh, well.
It’s a literary allusion. As a teenager, Harry would frequently have a boner in his hand, bringing him up to 33.
Yes, it is possible to fanwank nearly anything.
Indeed. 
Apparently one can get up to three sesamoid bones in the hand in addition to the regular bones.
I thought this thread was going to be about what Hermione was thinking after she took the polyjuice potion in Book 7 and became a fully-equipped Harry.
Wizards have 6 fingers. Well known fact. Who’d have thought that JKR’s writings were so subtle?