Clubbing of Fingers

Clubbing of the fingernail. The red line shows the outline of a clubbed nail.

Clubbing develops in five steps:

1. Fluctuation and softening of the nail bed (increased ballotability)
2. Loss of the normal <165° angle (Lovibond angle) between the nailbed and the fold (cuticula)
3. Increased convexity of the nail fold
4. Thickening of the whole distal (end part of the) finger (resembling a drumstick)
5. Shiny aspect and striation of the nail and skin

Schamroth's test or Schamroth's window test  is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly opposed (place fingernails of same finger on opposite hands against each other, nail to nail), a small diamond-shaped "window" is normally apparent between the nailbeds. If this window is obliterated, the test is positive and clubbing is present.