M16.31 identifies unilateral osteoarthritis of the right hip that developed as a direct consequence of hip dysplasia — distinct from primary or post-traumatic OA — and is fully billable for FY2026.

Documentation tips

What should appear in the chart to support M16.31.

Source · Editorial brief grounded in 6 cited references ↓

• Explicitly document the causal relationship: note that the right hip OA developed as a result of hip dysplasia, not as primary or post-traumatic OA.
• Include imaging findings that confirm both the dysplastic anatomy (e.g., lateral center-edge angle, acetabular index) and the OA changes (joint space narrowing, osteophytes, subchondral sclerosis).
• Specify laterality as 'right hip' by name in the assessment and plan — do not rely on the imaging report alone to establish it.
• Document conservative care history (physical therapy, activity modification, NSAIDs, intra-articular injections) to support medical necessity if THA authorization is anticipated.
• If congenital hip dysplasia has previously been coded (Q65.xx), ensure continuity in the record connecting that history to the current degenerative diagnosis.

Related CPT procedures

Procedure codes commonly billed with M16.31. 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 M16.31 and adjacent codes.

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

• Using M16.11 (unilateral primary OA, right hip) when the chart documents a dysplastic etiology — these are distinct etiologic categories and incorrect code selection can cause authorization mismatches for THA.
• Billing the non-billable parent M16.3 instead of the laterality-specific child code M16.31; most payers require the billable, specific code.
• Failing to distinguish M16.31 (OA caused by dysplasia) from Q65.xx (congenital hip dysplasia without stated OA) — if both diagnoses are active and documented, both codes may be appropriate as dual diagnoses.
• Assuming M16.31 applies to left-hip dysplastic OA — left hip maps to M16.32; swapping laterality creates a clinical-record mismatch that flags on audit.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M16.3 (laterality / anatomic variants).