Primary osteoarthritis affecting a joint site that does not have its own dedicated ICD-10-CM code — a residual category within M19.0 for idiopathic, non-traumatic, non-secondary degenerative joint disease at locations such as the temporomandibular joint, sacroiliac joint, or acromioclavicular joint.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 15
- Region
- Other
Documentation tips
What should appear in the chart to support M19.09.
Source · Editorial brief grounded in 4 cited references ↓
- Name the specific joint explicitly in the assessment (e.g., 'primary osteoarthritis of the right acromioclavicular joint') — M19.09 has no laterality subcode, so the site is preserved only in the note.
- Confirm there is no dedicated M19.0x subcategory for the joint before defaulting to M19.09; shoulder, elbow, wrist, hand, and ankle/foot each have their own codes.
- Distinguish primary from post-traumatic (M19.19) and secondary (M19.29) OA in the assessment — all three have an 'other specified site' code, and etiology drives the selection.
- Document imaging findings that support degenerative joint disease — joint space narrowing, subchondral sclerosis, osteophyte formation — to substantiate the diagnosis at an atypical site.
- If the spine is involved, route to M47 and do not use M19.09; document spinal versus peripheral joint involvement clearly.
Related CPT procedures
Procedure codes commonly billed with M19.09. 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 M19.09 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Coding M19.09 when the affected joint is the hip (M16), knee (M17), or first CMC joint (M18) — those have their own category codes and M19.09 is incorrect for them.
- Using M19.09 interchangeably with M19.91 (unspecified site) — M19.09 requires a documented joint name; M19.91 is for undocumented or unknown sites.
- Applying M19.09 to spinal osteoarthritis — the tabular Type 2 Excludes directs spine OA to M47, making M19.09 a coding error for any vertebral level.
- Overlooking M20.2 (hallux rigidus) when the provider documents OA of the first MTP joint — that condition has its own code and is excluded from M19.
- Failing to capture laterality anywhere in the record; because M19.09 lacks a laterality subcode, the specific side must be documented in the clinical note to support medical necessity.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
M19.09 is the correct code when the physician documents primary (idiopathic) osteoarthritis at a joint that falls outside every other named M19.0x subcategory — which cover shoulder (M19.01x), elbow (M19.02x), wrist (M19.03x), hand (M19.04x), and ankle/foot (M19.07x). If the affected joint is the hip, use M16; knee, use M17; first CMC joint, use M18. Spine osteoarthritis routes to M47, not M19. M19.09 is the last-resort specific code — 'other specified' means the site is documented and identified, just not individually enumerated in the tabular.
Do not confuse M19.09 with M19.91 (primary osteoarthritis, unspecified site). M19.91 is for cases where the site is genuinely unknown or undocumented. M19.09 requires that the clinician has named a specific joint — it simply lacks its own dedicated subcategory. If documentation says 'osteoarthritis of the acromioclavicular joint' or 'OA of the sacroiliac joint,' M19.09 is the right pick.
Note the Type 2 Excludes under M19: polyarthritis maps to M15, hallux rigidus maps to M20.2, and all spinal arthrosis maps to M47. These cannot be coded with M19.09. Because M19.09 carries no laterality subcode, document the specific joint name in the medical record — that detail lives in the note, not the code itself.
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01Which joints most commonly get coded to M19.09?
02Can I use M19.09 for glenohumeral (shoulder) osteoarthritis?
03Does M19.09 require a 7th character extension?
04What is the difference between M19.09 and M19.91?
05Can M19.09 be coded alongside M15 polyarthritis codes?
06Is M19.09 valid for sacroiliac joint osteoarthritis?
07How does M19.09 interact with spine codes?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (FY2026, effective Oct 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M15-M19/M19-/M19.09
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M19.09
- 04unboundmedicine.comhttps://www.unboundmedicine.com/icd/view/ICD-10-CM/1429231/1/M19_09___Primary_osteoarthritis_other_specified_site
Mira AI Scribe
The Mira AI Scribe captures the specific joint name, laterality, and OA etiology (primary/idiopathic versus post-traumatic or secondary) directly from the provider's assessment. It also flags imaging references — joint space narrowing, osteophyte formation, subchondral changes — and any conservative treatment history. This prevents the claim from dropping to M19.91 (unspecified site), which signals incomplete documentation and can trigger payer audit or medical-necessity denial.
See how Mira captures M19.09 documentation