ICD-10-CM · Hip

M16.10

Primary (idiopathic) osteoarthritis affecting one hip, with the specific side not documented or not determinable from the clinical record.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 14
Region: Hip

Drawn from CDCCMSAAOSAAPCICD

Documentation tips

What should appear in the chart to support M16.10.

Source · Editorial brief grounded in 5 cited references ↓

Name the affected side explicitly in the assessment — 'right hip' or 'left hip' — so M16.11 or M16.12 can be used instead of the unspecified M16.10.
Record imaging findings that support primary OA: joint space narrowing, subchondral sclerosis, osteophyte formation, or Kellgren-Lawrence grade on X-ray (CPT 73502/73522 series).
Distinguish primary from secondary OA in the note — document the absence of prior trauma, dysplasia, or inflammatory disease when billing M16.10 rather than a secondary OA code.
If billing a laterally specific procedure (injection, nerve block, arthroplasty), confirm the diagnosis code laterality matches; a mismatch between M16.10 and a right-specific CPT is a common denial trigger.
Document functional limitation (gait disturbance, limited ROM, ADL impact) and any conservative care attempted — payers increasingly require this for surgical or interventional prior authorizations.
Update the code at follow-up if laterality becomes documented; do not carry forward M16.10 indefinitely when the record now clearly identifies the affected hip.

Related CPT procedures

Procedure codes commonly billed with M16.10. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

27130 $1,162.02

Primary total hip arthroplasty replacing both the acetabular socket and proximal femoral components with prosthetic implants, with or without bone graft.

27132 $1,504.04

Conversion of a previously operated hip — any prior surgery except total hip arthroplasty — to a complete total hip arthroplasty, replacing both femoral and acetabular components, with or without bone graft.

27134 $1,695.43

Revision of total hip arthroplasty involving replacement of both the femoral and acetabular components in a single operative session.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

73501 $33.73

Single-view X-ray of one hip, including the pelvis when clinically indicated — the minimum imaging study in the hip radiograph family.

73502 $48.77

Radiologic exam of a single hip, capturing two or three views, including the pelvis when performed.

73503 $62.79

Radiologic examination of a single hip, including the pelvis when performed, capturing a minimum of four views from different angles.

73521 $41.75

Bilateral hip X-ray examination capturing two radiographic views of both hips, including the pelvis when performed.

73523 $61.46

Radiologic examination of both hips, including the pelvis when performed, requiring a minimum of five views captured from multiple projections.

97110 $29.06

Therapeutic exercise billed per 15-minute unit, targeting strength, endurance, range of motion, or flexibility with direct one-on-one patient contact.

97140 $27.72

Skilled, hands-on manual therapy techniques — including joint mobilization/manipulation, manual lymphatic drainage, and manual traction — applied to one or more body regions, billed per 15-minute unit.

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

64447 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M16.10 and adjacent codes.

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

Using M16.10 when the note documents 'right' or 'left' hip — that forces a downgrade to unspecified specificity and can reduce reimbursement or trigger a payer compliance flag; use M16.11 or M16.12 instead.
Confusing M16.10 (unilateral, unspecified side) with M16.9 (osteoarthritis of hip, unspecified) — M16.9 does not even specify unilateral vs. bilateral, making it a lower-specificity fallback than M16.10.
Applying M16.10 to secondary OA presentations — post-traumatic hip OA belongs in M16.5-, dysplasia-related OA in M16.3-, and other secondary OA in M16.7, regardless of whether laterality is specified.
Pairing M16.10 with a laterally specific procedure code (e.g., right-hip total arthroplasty CPT 27130) without reconciling the laterality mismatch — this is a common audit flag and denial reason.
Selecting M16.10 based on a working diagnosis when imaging has already confirmed the side — once the record supports specificity, the unspecified code is no longer defensible.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M16.10 is the fallback code within the M16.1- subcategory when the provider documents unilateral primary hip OA but fails to specify right or left. It sits one level below the non-billable parent M16.1 and one level above the fully specific codes M16.11 (right) and M16.12 (left). CMS and AAOS guidance both flag unspecified codes as lowest-preference: use M16.10 only when laterality is genuinely absent from the documentation — not as a shortcut when the note says 'right' or 'left.'

Primary (idiopathic) OA is distinguished from secondary OA by the absence of an underlying cause. If the OA follows a prior hip fracture, use the M16.5- post-traumatic series. If it stems from hip dysplasia, use M16.3-. If it is secondary to another identifiable condition (obesity, inflammatory arthropathy), use M16.7 and code the underlying condition separately. M16.10 is not appropriate for any of those scenarios, even if laterality is unspecified.

For payer and LCD compliance — particularly when billing nerve blocks (e.g., CPT 64447) or joint injections (CPT 20610) — diagnosis-procedure linkage must be airtight. Payers have denied claims when unspecified hip OA codes are paired with laterally specific procedures; if the op note or pre-procedure assessment names the hip, the diagnosis code must match.

Sibling codes

Other billable codes under M16.1 (laterality / anatomic variants).

M16.11

Unilateral primary osteoarthritis, right hip

M16.12

Unilateral primary osteoarthritis, left hip

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01When is M16.10 the correct code rather than M16.11 or M16.12?

Use M16.10 only when the clinical documentation genuinely does not specify which hip is affected. If the note, imaging report, or operative consent names the right or left hip, assign M16.11 or M16.12 respectively — M16.10 is a true last resort, not a shortcut.

02What is the difference between M16.10 and M16.9?

M16.10 specifies that the OA is unilateral and primary but the side is unknown. M16.9 (Osteoarthritis of hip, unspecified) conveys even less information — it does not indicate unilateral vs. bilateral or primary vs. secondary. M16.10 is always more specific than M16.9 for a documented unilateral primary presentation.

03Can M16.10 be used for post-traumatic hip OA when the side isn't documented?

No. Post-traumatic hip OA maps to M16.50 (unilateral post-traumatic osteoarthritis, unspecified hip), not M16.10. The M16.1- subcategory is reserved for primary (idiopathic) OA; etiology drives the code selection before laterality does.

04Why are claims for CPT 64447 being denied when paired with M16.10 or M16.11?

Payers deny CPT 64447 (femoral nerve block) when the diagnosis-procedure linkage isn't supported by an applicable LCD or when the billed diagnosis doesn't match the treated side. Confirm your MAC's LCD for hip OA nerve blocks and ensure the diagnosis code laterality matches the procedural documentation.

05Does M16.10 require a 7th-character extension?

No. M-codes in Chapter 13 do not use 7th-character extensions. The A/D/S extension convention applies to injury codes (S-codes). M16.10 is complete as a 5-character code.

06Should M16.10 ever appear on a total hip arthroplasty claim?

It should not if laterality is documented anywhere in the chart. CPT 27130 (total hip arthroplasty) is inherently side-specific; using M16.10 alongside it creates a laterality mismatch that auditors and payers flag. Use M16.11 or M16.12 to match the operative side.

07How does M16.10 interact with DRG assignment for hip replacement?

The diagnosis code feeds DRG grouping alongside the CPT/ICD-10-PCS procedure code. An unspecified diagnosis like M16.10 paired with a laterally specific procedure can cause grouper logic inconsistencies and may affect DRG 470/471 assignment accuracy — another reason to resolve laterality before the claim drops.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 — https://icd10cmtool.cdc.gov/
02CMS ICD-10 Clinical Concepts for Orthopedics — https://www.cms.gov/medicare/coding/icd10/downloads/icd10clinicalconceptsorthopedics1.pdf
03AAOS Resident Guide: ICD-10 — https://www.aaos.org/globalassets/quality-and-practice-resources/coding-and-reimbursement/resident-guide/resident-guide_icd10.pdf
04AAPC Orthopedic Coding Alert: Bone Up on Rules for Osteoarthritis Dx Coding — https://www.aapc.com/codes/coding-newsletters/my-orthopedic-coding-alert/icd-10-coding-bone-up-on-rules-for-osteoarthritis-dx-coding-171931-article
05ICD10Data.com 2026 M16.0 adjacency table — https://www.icd10data.com/ICD10CM/Codes/M00-M99/M15-M19/M16-/M16.0

Mira AI Scribe

Mira AI Scribe captures the affected hip by name, the character of OA (primary/idiopathic vs. secondary), imaging findings (joint space narrowing, osteophyte formation, Kellgren-Lawrence grade), and any prior conservative care. That documentation locks in M16.11 or M16.12 instead of the fallback M16.10, preventing laterality-based denials when paired with injection, nerve block, or arthroplasty procedure codes.

See how Mira captures M16.10 documentation