Bones Variation
Accessory ossicles
Small extra bones, most often in the foot, that form when a growth centre never fuses with its main bone. They are harmless but can be mistaken for fractures on an X-ray.
Up to 1 in 5 feet
Bones and joints
Cracking, bending, extra bones, missing bones, and joint flexibility.
11 oddities. 11 have this as their primary region.
Bones Variation
Cervical rib
An extra rib above the normal top rib, growing from the lowest bone in the neck. About 1 in 100 people have one, and most never know.
About 1% of people
Bones Variation
Clinodactyly
A finger that curves sideways toward its neighbours, most often the little finger leaning toward the ring finger. Between 1% and 20% of people have it, and on its own it is harmless.
1–20% of people
Bones Variation
Hitchhiker's thumb
A thumb whose top joint bends back past 50 degrees, once taught as a simple recessive gene. Thumb angle is really a smooth range, and the genetics are not that simple.
24–36% of people
Bones Variation
Joint hypermobility
About 1 in 5 people have joints that bend further than usual, measured with a nine-point test called the Beighton score. For most people it causes no trouble.
10–25% of people
Bones Trick
Knuckle cracking
Pulling or bending a finger joint until it pops. Between 25% and 54% of people do it out of habit. The sound is a gas bubble forming in the joint fluid, and it does not cause arthritis.
25–54% crack habitually
Bones Trick
Midtarsal break
A foot that bends in the middle, between the heel and the ball, as well as at the toes. About 1 in 13 people have it. It is a leftover from tree-climbing ancestors.
About 1 in 13 (7.7%)
Bones Variation
Morton's toe
A second toe that looks longer than the big toe because the first metatarsal bone in the foot is short. It is common, and it is the foot shape seen on classical Greek statues.
3–22% of people
Bones Variation
Torus palatinus
A hard bony lump along the midline of the roof of the mouth that grows slowly and is completely harmless. Many people find it by chance and worry that it is a tumour.
About 20% of people
Bones Trick
Voluntary joint dislocation
Pushing a joint partly or fully out of its socket on purpose, then back in. About 20% of people have some joint hypermobility. True voluntary dislocation is much rarer and often linked to a connective tissue disorder.
Rare; no formal count Icky
Bones Variation
Webbed toes
Two toes joined by skin, most often the second and third, in about 1 in 2,000 to 3,000 babies. The toes usually work normally and many people leave them as they are.
About 1 in 2,000–3,000 births