M19.93

Secondary osteoarthritis at an unspecified anatomic site — osteoarthritis arising from an identifiable underlying cause when the affected joint is not documented.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 9
Region: General

Drawn from CDCICD10DataAAPCCMS

Documentation tips

What should appear in the chart to support M19.93.

Source · Editorial brief grounded in 5 cited references ↓

Identify the causative condition explicitly in the note — e.g., 'secondary OA due to prior tibial plateau fracture' — so both M19.93 and the etiology code are defensible.
If the joint is identifiable anywhere in the encounter note (imaging report, exam findings, procedure note), use the site-specific secondary OA code instead of M19.93.
Record imaging findings (joint space narrowing, subchondral sclerosis, osteophytes) and link them to the documented underlying cause to support the 'secondary' classification over primary or post-traumatic.
Sequence the secondary OA code first, then the underlying etiology code (e.g., obesity, metabolic disorder, prior arthropathy), per ICD-10-CM convention for manifestation/etiology pairs.
Document the absence of laterality or multi-joint involvement when M19.93 is intentionally chosen — this protects against a query that the site was simply omitted.

Related CPT procedures

Procedure codes commonly billed with M19.93. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

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.

99203 $117.57

New patient office or outpatient visit requiring a medically appropriate history and/or examination with low-complexity medical decision-making, or 30–44 minutes of total provider time on the date of the encounter.

99204 $177.36

New patient office or outpatient visit requiring moderate medical decision making, or 45–59 minutes of total provider time on the date of the encounter.

27447 $1,159.35

Knee replacement surgery addressing both the medial and lateral tibiofemoral compartments, with or without resurfacing of the patella.

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.

29827 $976.31

Arthroscopic surgical repair of the rotator cuff, performed entirely through the shoulder joint via endoscopic technique.

73564 $49.43

Radiologic examination of the knee consisting of four or more views, including oblique and tunnel projections, for a complete diagnostic workup.

73721 $204.41

MRI of a lower extremity joint (hip, knee, or ankle) performed without contrast material.

Common coding pitfalls

The recurring mistakes coders make with M19.93 and adjacent codes.

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

Using M19.93 when the joint is documented elsewhere in the chart — if the note or imaging report names the joint, a site-specific secondary OA code is required.
Reporting M19.93 without the underlying etiology code — secondary OA by definition has a cause; the claim is incomplete without it.
Confusing M19.93 (secondary, unspecified site) with M19.90 (unspecified OA, unspecified site) or M19.91 (primary OA, unspecified site) — the type of OA drives the code selection, not just the missing laterality.
Applying M19.93 to spinal OA — osteoarthritis of the spine is coded under M47 (Spondylosis), not M15–M19.
Defaulting to M19.93 for generalized multi-joint OA — polyosteoarthritis belongs in the M15 category, not M19.93.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M19.93 is the fallback code for secondary osteoarthritis when the physician documents a causative condition (trauma history, prior surgery, metabolic disease, obesity, inflammatory arthropathy, etc.) but does not specify which joint is affected. Because secondary OA requires a known etiology, you must also report the underlying primary condition — for example, morbid obesity (E66.01), prior fracture sequela (S-code with 7th character S), or rheumatoid arthritis. Failure to code both diagnoses leaves the claim clinically incomplete and exposes it to audit challenge.

M19.93 sits at the bottom of a well-structured specificity ladder. When the joint is known, use site-specific secondary OA codes instead: M19.21x (hand), M17.4/M17.5 (knee), M16.3x/M16.5 (hip), M19.07x/M19.17x (ankle/foot), and so on. Reserve M19.93 only when the operative or office note genuinely omits joint identification — not as a convenience default. Payers and RAC auditors treat unspecified-site OA codes as audit magnets when the same encounter includes a joint-specific procedure code.

For MS-DRG assignment, M19.93 maps to DRG 553 (Bone Diseases and Arthropathies with MCC) or DRG 554 (without MCC), so accurate CC/MCC capture on the underlying etiology code can directly affect reimbursement weight.

Inclusion & exclusion notes

Per the official ICD-10-CM Tabular List.

Source · CDC ICD-10-CM Official Tabular List · 2026

Includes

Secondary osteoarthritis NOS

Sibling codes

Other billable codes under M19.9 (laterality / anatomic variants).

M19.92

Post-traumatic osteoarthritis, unspecified site

M19.91

Primary osteoarthritis, unspecified site

M19.90

Unspecified osteoarthritis, unspecified site

Frequently asked questions

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

01When is M19.93 actually the correct code versus a more specific secondary OA code?

Use M19.93 only when the provider documents that OA is secondary (causative condition present) but genuinely fails to name the affected joint anywhere in the encounter note, imaging reports, or procedure documentation. If any part of the record identifies the joint, assign the site-specific secondary OA code.

02Do I need to report the underlying cause as a separate code with M19.93?

Yes. Secondary OA requires dual coding. Report the etiology first or as an additional diagnosis per payer convention — for example, E66.01 for morbid obesity or an S-code with 7th character S for a fracture sequela. A standalone M19.93 without the cause is clinically incomplete.

03How does M19.93 differ from M19.90 and M19.91?

M19.90 is unspecified OA at an unspecified site — type unknown. M19.91 is primary OA at an unspecified site — degenerative, no identifiable cause. M19.93 is secondary OA at an unspecified site — a causative condition is documented. All three lack joint specificity, but the OA type drives which code you assign.

04Can M19.93 be used for knee or hip OA when the surgeon doesn't specify laterality?

No. Once the joint is identified as knee or hip, you must use a knee-specific (M17.x) or hip-specific (M16.x) secondary OA code, even if laterality is unspecified. M19.93 is for encounters where the joint itself is undocumented.

05Does M19.93 apply to spinal osteoarthritis?

No. Osteoarthritis of the spine is classified under M47 (Spondylosis). The M15–M19 block, including M19.93, covers peripheral joints only. Using M19.93 for back or neck OA is a coding error.

06What MS-DRGs does M19.93 map to, and does the underlying etiology code affect reimbursement?

M19.93 maps to MS-DRG 553 (with MCC) or 554 (without MCC) under v43.0. The etiology code you pair with it may carry CC or MCC status, directly affecting the DRG weight and reimbursement — so accurate dual coding matters financially, not just clinically.

07Is M19.93 a valid primary diagnosis on a professional claim for an orthopedic office visit?

Yes, it is billable and specific per the FY2026 ICD-10-CM tabular list. However, payers may scrutinize it when paired with a joint-specific E/M or procedure code, since the mismatch signals possible underdocumented specificity. Always query the physician if joint identity is recoverable from the note.

Sources & references

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

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M15-M19/M19-/M19.93
03
aapc.com
https://www.aapc.com/codes/icd-10-codes/M19.93
04
aapc.com
https://www.aapc.com/codes/coding-newsletters/my-orthopedic-coding-alert/icd-10-coding-bone-up-on-rules-for-osteoarthritis-dx-coding-171931-article
05
cms.gov
https://www.cms.gov/medicare/coding/icd10/downloads/icd10clinicalconceptsorthopedics1.pdf

Mira AI Scribe

Mira AI Scribe captures the causative condition (prior trauma, metabolic disease, inflammatory arthropathy, obesity), the treating provider's statement that the OA is secondary rather than primary, and any imaging evidence of degenerative joint changes. If the scribe identifies a joint name in the note, it flags the coder to upgrade to a site-specific code — preventing unspecified-site downcoding and the audit risk that follows when a procedure code names a joint but the diagnosis does not.

See how Mira captures M19.93 documentation