ICD-10-CM 2027
ICD-10 code for flexion deformity
From the official ICD-10-CM alphabetic index entry “Deformity › flexion (joint) (acquired)”. Page updated September 29, 2026.
About coding flexion deformity
The ICD-10-CM code for flexion deformity is M21.20 (Flexion deformity, unspecified site). The official index lists 2 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on M21.20.
Within M21.2, choose M21.20 (unspecified site) only when documentation doesn't support a more specific option: shoulder (M21.21), elbow (M21.22), wrist (M21.23), finger joints (M21.24), hip (M21.25), knee (M21.26) and ankle and toes (M21.27).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 564 (Other Musculoskeletal System and Connective Tissue Diagnoses with MCC, relative weight 1.4908), DRG 565 (Other Musculoskeletal System and Connective Tissue Diagnoses with CC, relative weight 0.9783) and DRG 566 (Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC, relative weight 0.7378), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific flexion deformity codes (official index)
Common questions about flexion deformity ICD-10 codes
What is the ICD-10 code for flexion deformity?
- M21.20 — Flexion deformity, unspecified site. More specific codes apply when the documentation supports them: Q74.9, Q65.89.
What is the ICD-10 code for congenital nos flexion deformity?
- Q74.9 — Unspecified congenital malformation of limb(s).
Is M21.20 billable?
- Yes. M21.20 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can M21.20 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict M21.20 as a principal diagnosis.
Is M21.20 a CC or MCC?
- No. M21.20 is neither a CC nor an MCC under MS-DRG v44.0.