M21.171 Varus deformity, not elsewhere classified, right ankle

Billable ICD-10-CM code, FY2026.

Applies from M21 Other acquired deformities of limbs

Excludes1 (never code together)

• acquired absence of limb (Z89.-)
• congenital absence of limbs (Q71-Q73)
• congenital deformities and malformations of limbs (Q65-Q66, Q68-Q74)

Excludes2 (not included here)

• acquired deformities of fingers or toes (M20.-)
• coxa plana (M91.2)

Applies from M21.1 Varus deformity, not elsewhere classified

Excludes1 (never code together)

• metatarsus varus (Q66.22-)
• tibia vara (M92.51-)

MS-DRG index

Defines the logic of DRG(s) 564-566 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 736.71 Acquired equinovarus deformity (approximate)

Code annotations containing back-references to M21.171

Back-references to M21.1

• Type 1 Excludes: Q66 Congenital deformities of feet ("varus deformities (acquired) (M21.1-)")

Back-references to M21

• Type 1 Excludes: M23 Internal derangement of knee ("deformity of knee (M21.-)")
• Type 2 Excludes: M24.5 Contracture of joint ("acquired deformities of limbs (M20-M21)")
• Type 2 Excludes: M25 Other joint disorder, not elsewhere classified ("acquired deformities of limb (M20-M21)")
• Type 2 Excludes: M95 Other acquired deformities of musculoskeletal system and connective tissue ("acquired deformities of limbs (M20-M21)")
• Type 1 Excludes: Z89 Acquired absence of limb ("acquired deformities of limbs (M20-M21)")

Nearby codes

• M21.16 Varus deformity, not elsewhere classified, knee
• M21.161 Varus deformity, not elsewhere classified, right knee
• M21.162 Varus deformity, not elsewhere classified, left knee
• M21.169 Varus deformity, not elsewhere classified, unspecified knee
• M21.17 Varus deformity, not elsewhere classified, ankle
• M21.171 Varus deformity, not elsewhere classified, right ankle (this code)
• M21.172 Varus deformity, not elsewhere classified, left ankle
• M21.179 Varus deformity, not elsewhere classified, unspecified ankle
• M21.2 Flexion deformity
• M21.20 Flexion deformity, unspecified site
• M21.21 Flexion deformity, shoulder