M21Other acquired deformities of limbs

M21 is the ICD-10-CM diagnosis code for other acquired deformities of limbs. It belongs to block M20-M25 (other joint disorders) and chapter 13 (diseases of the musculoskeletal system and connective tissue). It is a header code, so it can't be reported by itself; one of its 10 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: M21.0 (classified), M21.1 (classified), M21.2 (deformity), M21.3 ((acquired)), M21.4 ((acquired)), M21.5 (clubfoot), M21.6 (foot), M21.7 ((acquired)) and 2 more.

Don't report M21 together with the conditions in its Excludes1 note: acquired absence of limb (Z89.-), congenital absence of limbs (Q71-Q73) and congenital deformities and malformations of limbs (Q65-Q66, Q68-Q74).

The conditions in its Excludes2 note aren't part of M21, but may be coded alongside it if the patient has both: acquired deformities of fingers or toes (M20.-) and coxa plana (M91.2).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.