Clinodactyly
Also called: Curved little finger · Bent pinky
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.
How common
Do you have this?
How it works
Each finger apart from the thumb has three small bones called phalanges. The middle one is normally a short rectangle. In clinodactyly the middle bone is wedge-shaped, shorter on one side than the other4. The bone above it tilts toward the short side, so the fingertip points sideways. Many doctors count it when the curve is more than 10 degrees from straight4. There is no agreed cutoff1. The little finger is affected most often, and it usually leans toward the ring finger.
The shape is set before birth and does not get worse after the bones stop growing. It is usually on both hands. It can run in families as a dominant trait, so a parent may have it too1. Most people with a slight bend never notice it.
A bent little fingertip is one of the many small physical signs seen in Down syndrome2. Together, these signs can make doctors suspect it at birth2. That link worries some parents. On its own, in a person with no other signs, a curved little finger means nothing beyond a curved little finger1.
A different condition, camptodactyly, is a finger bent forward at the middle joint that cannot straighten fully. Its exact cause is unknown, but a weak small muscle in the hand and faulty tendons can play a part3.
How common it is
The 1% to 20% range comes from studies that use different angle cutoffs on different populations, not from one consistent count1. Mild curves are common1. It is much more common in people with Down syndrome. About 57% of them have a bent little fingertip2. The true rate is not known4.
Try it
- Lay one hand flat on a table with the fingers together.
- Look at the little finger from above. In most people it lies straight. In clinodactyly the top two segments angle toward the ring finger.
- Spread the fingers. The curve stays, because it is in the bone and not the joint.
- Check the other hand. Both hands usually match.
Is it a problem?
No, not on its own. A curved little finger with no other signs is a normal variation and needs no treatment1. It is not proof of Down syndrome. Doctors treat clinodactyly as one clue among many physical signs, never as a diagnosis by itself2.
See a doctor if the curve:
- is severe enough to affect grip,
- appeared suddenly rather than from birth,
- comes with other unusual features.
That combination is worth a proper look.
Sources and further material
- Wikipedia Clinodactyly
- Wikipedia Down syndrome
- NCBI Clinodactyly (StatPearls) Clinical reference. Defines the 10-degree cutoff and the wedge-shaped bone.
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Related oddities
Camptodactyly
A finger that stays bent forward at its middle joint and cannot fully straighten, usually the little finger. Under 1% of people have it. Mild cases rarely cause trouble, but the bend can get worse while a child grows.
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.
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.
Webbed toes
Two toes joined by skin, most often the second and third, in about 1 in 2,000 to 2,500 babies. The toes usually work normally and many people leave them as they are.