Arthritis affecting multiple anatomical sites that falls under a specified type but does not fit any more precisely defined ICD-10-CM category — used when the arthritis type is documented but no single-site or disease-specific code applies.

Documentation tips

What should appear in the chart to support M13.89.

Source · Editorial brief grounded in 6 cited references ↓

• Name every affected joint explicitly — 'bilateral knees and right hip' rather than 'multiple joints' — so the multiple-site designation is chart-supported.
• Document the arthritis type or qualifying descriptor (e.g., allergic, climacteric, post-traumatic) that differentiates this from unspecified polyarthritis (M13.0).
• Record why a more specific code (M15.x for OA, M06.x for rheumatoid, etc.) does not apply — a brief sentence ruling out common types protects against query and audit.
• Include imaging findings (X-ray, MRI) or lab results that support arthritis at each named site; absence of evidence supporting multi-site involvement is the most common audit flag.
• If conservative treatment has been trialed, list the interventions and response — payers may require evidence of medical necessity before authorizing further workup or joint procedures.

Related CPT procedures

Procedure codes commonly billed with M13.89. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M13.89 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Using M13.89 when the provider has documented osteoarthritis at multiple sites — M15.0 (primary generalized osteoarthritis) or M15.3 is the correct code in those cases.
• Defaulting to M13.89 when the provider documents 'inflammatory arthritis' affecting multiple joints — verify whether M06.09 (rheumatoid arthritis, multiple sites) or another specific inflammatory category applies before using M13.89.
• Coding M13.89 when only a single joint is involved — use the site-specific M13.8x code with laterality instead.
• Confusing M13.89 with M13.0 (polyarthritis, unspecified): M13.0 is for polyarthritis with no type identified at all; M13.89 requires that a specific arthritis type is documented but does not have a more precise home in ICD-10-CM.
• Failing to review Excludes1/Excludes2 annotations at the M13 category level before assigning M13.89 — certain infectious and metabolic arthropathies are excluded and must be coded from their own chapters.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M13.8 (laterality / anatomic variants).