Camptodactyly

How it works

In camptodactyly, the middle joint of a finger is bent toward the palm and cannot fully straighten⁴. Doctors call it the proximal interphalangeal joint. The little finger is affected most often³⁴.

The cause is usually in the soft tissues rather than the bone. Most often a small palm muscle, a lumbrical, is attached in the wrong place. The tendon that bends the finger can also be tight².

Doctors describe three types⁵. Type I starts in infancy. Type II starts in the teenage years and affects more girls than boys. Both usually involve only the little finger². Type III is present at birth, bends several fingers, and is usually part of a syndrome²⁵.

It can run in families¹. The bend can get worse over time, often during growth spurts⁴.

Clinodactyly curves the finger sideways, because the middle bone is wedge-shaped. Camptodactyly bends it forward, because of the soft tissues².

How common it is

No study has counted camptodactyly in the general population. The best figure comes from one UK neurology clinic. Over ten years, it found camptodactyly in 0.43% of almost 10,000 outpatients¹. Cases were recorded when noticed, not by checking every hand¹. These patients are not a true sample of everyone. All had the isolated form, and all but one had no symptoms¹. Hospital pages and case reports say “less than 1%” without citing a count³⁴. The bend is more often on both hands than on one¹.

Try it

1. Lay one hand flat on a table, palm down, with the fingers together.
2. Look at the little finger from the side. In most people it lies flat.
3. In camptodactyly the middle joint stays lifted and the fingertip points down.
4. Look from above. A finger that leans sideways toward the ring finger is clinodactyly instead.
5. With the other hand, press the middle joint down very gently. Some bent fingers straighten with help, others stay stiff². Never force it.
6. Check the other hand. Both can be bent, by different amounts¹.

Is it a problem?

Usually not. It rarely hurts, and in most cases it does not affect how the hand works⁴. A bend under 30 degrees that does not affect the hand counts as mild⁴. See a doctor if the bend gets worse, especially in a child during a growth spurt. Also see one if it affects grip, if several fingers are bent, or if other unusual signs come with it. A bend at the top joint or at the knuckle is a different pattern, and may come from an injury³. Trigger finger and Dupuytren’s disease can look similar, so a doctor needs to tell them apart².