M21.9Unspecified acquired deformity of limb and hand

M21.9 is the ICD-10-CM diagnosis code for unspecified acquired deformity of limb and hand. It belongs to category M21 (other acquired deformities of limbs), 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 6 subcodes must be used instead.

Within M21, choose M21.9 (Unspecified acquired deformity of limb and hand) only when documentation doesn't support a more specific option: valgus deformity, not elsewhere classified (M21.0), varus deformity, not elsewhere classified (M21.1), flexion deformity (M21.2), wrist or foot drop (acquired) (M21.3), Flat foot [pes planus] (acquired) (M21.4), acquired clawhand, clubhand, clawfoot and clubfoot (M21.5), other acquired deformities of foot (M21.6), unequal limb length (acquired) (M21.7) and 1 more.

To report this condition, pick the subcode that matches the documentation: M21.90 (limb), M21.92 (arm), M21.93 (forearm), M21.94 (hand), M21.95 (thigh) and M21.96 (leg).

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