M21.731 Unequal limb length (acquired), right ulna

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 M21.7 Unequal limb length (acquired)

Notes

• The site used should correspond to the shorter limb

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• 736.89 Other acquired deformity of other parts of limb (approximate)

Code annotations containing back-references to M21.731

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

• M21.72 Unequal limb length (acquired), humerus
• M21.721 Unequal limb length (acquired), right humerus
• M21.722 Unequal limb length (acquired), left humerus
• M21.729 Unequal limb length (acquired), unspecified humerus
• M21.73 Unequal limb length (acquired), ulna and radius
• M21.731 Unequal limb length (acquired), right ulna (this code)
• M21.732 Unequal limb length (acquired), left ulna
• M21.733 Unequal limb length (acquired), right radius
• M21.734 Unequal limb length (acquired), left radius
• M21.739 Unequal limb length (acquired), unspecified ulna and radius
• M21.75 Unequal limb length (acquired), femur