This arrangement keeps the skin of the palm from sliding around like a rubber glove when we use our hands to grip and twist. In some people, this layer of fascia shrinks and thickens, leading to Dupuytren's disease . When one curls the fingers into a fist, the fingertips naturally group together side by side. If the fingertips all bend together, they continue into the palm side by side. However, the natural tendency is for each fingertip to aim for the same point at the base of the thumb , which is obvious when touching each finger down to the base of the palm.
Fingers are never perfectly straight .
Usually, the index, ring and small finger each curve sideways slightly toward the middle finger, and the middle finger may curve toward either side. The finger bones are straight on the back side, but curved on the palm side . When we bend our fingers into a fist, the finger bones produce a shape similar to a circle in a square , round on the inside, square on the outside. When we make a fist, the fingertips curve through a spiral, not a circle . This is because the lengths of the finger bones are related in a way seen often in naturally occuring spirals.