The mysterious atrophied muscle, and no, I'm not talking about the generalized wasting of middle age.
The abductor digiti minimi (ADM) muscle of the foot is atrophied in many asymptomatic individuals. I used to worry about this being a sign of entrapment of the inferior calcaneal nerve, the first branch of the lateral plantar nerve. Here is an example of selective atrophy of the ADM:
My eyes were opened by an article by M. Recht et al. (AJR 2007; 189:W123-W127), who observed selective fatty atrophy of the abductor digiti minimi in 6.3% of examinations (38 patients out a total of 602 patients). Only one patient had their clinical management changed because of this finding.
Thus, I still mention this finding, but note that it can be seen in asymptomatic patients.
No need to cause a panic....