M05.80

Seropositive rheumatoid arthritis that does not fit the more specifically defined M05 subcategories, with the affected anatomical site undocumented or unspecified in the clinical record.

Verified May 8, 2026 · 7 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Multi-region

Drawn from CDCICD10DataAAPCCMSRhinomds

Documentation tips

What should appear in the chart to support M05.80.

Source · Editorial brief grounded in 7 cited references ↓

Document positive rheumatoid factor explicitly (e.g., RF titer, anti-CCP result) to justify any M05 code over seronegative M06 codes.
If a specific joint is examined or imaged, name it — this allows upgrade to a site-specific M05.8x code (e.g., M05.861 right knee, M05.851 right hip) instead of the unspecified M05.80.
Record whether the RA presentation involves organ complications (lung, heart, vasculitis, nodules); each has its own M05 subcategory and should not default to M05.80.
When M05.80 appears as a comorbidity on a surgical claim, document how the RA influenced surgical planning or perioperative management to support medical necessity.
Note disease activity status (remission, low, moderate, high) — though ICD-10-CM does not have a separate activity modifier, this language supports clinical appropriateness for biologics and DMARDs billed alongside the visit.

Related CPT procedures

Procedure codes commonly billed with M05.80. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

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.

27486 $1,274.91

Revision of a total knee arthroplasty involving a single component, performed with or without the use of donor bone graft material.

27487 $1,574.52

Revision total knee arthroplasty with replacement of both the femoral and tibial components, with or without the use of allograft tissue.

27134 $1,695.43

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

27137 $1,317.67

Revision of a total hip arthroplasty involving the acetabular component only, with or without autograft or allograft

27138 $1,367.10

Revision of total hip arthroplasty involving removal and replacement of the femoral component only, with or without bone graft.

20610 $68.81

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

86200 View procedure details

86235 View procedure details

Common coding pitfalls

The recurring mistakes coders make with M05.80 and adjacent codes.

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

Using M05.80 as the primary diagnosis for a joint-specific procedure (e.g., TKA, THA) when a site-specific M05.8x code is supported by the operative note — payers will expect laterality.
Defaulting to M05.80 when M05.9 (seropositive RA, unspecified) was intended: M05.80 is 'other' seropositive RA, not simply unspecified seropositive RA; use M05.9 when no subtype has been characterized at all.
Assigning M05.80 for RA of the spine — the Excludes 1 note at the M05 category level directs you to M45.- for spinal RA.
Failing to query the provider when a joint is mentioned in the note but laterality is missing — M05.80 should be a last resort, not a shortcut.
Confusing seronegative RA (M06.0x) with seropositive RA (M05.8x); RF lab status must be confirmed before coding any M05 code.

Clinical context

Source · Editorial summary grounded in 7 cited references ↓

M05.80 captures seropositive RA (positive rheumatoid factor) classified under the 'other' M05.8 subcategory when the provider has not documented a specific joint site or when the presentation spans diffuse, non-lateralizable involvement that cannot be assigned to a named joint code. It sits under the M05.8 parent, which covers seropositive RA presentations that do not map to the more granular M05 subcategories (e.g., M05.1x Felty syndrome, M05.2x RA lung disease, M05.3x RA vasculitis, M05.4x RA myopathy, M05.5x RA pericarditis, M05.6x RA endocarditis, M05.7x RA with rheumatoid nodules). If those organ-involvement subtypes are ruled out and the provider documents seropositive RA without naming a specific joint, M05.80 is the correct code.

For orthopedic coders, this code appears most often as a comorbidity on claims for joint replacement, synovectomy, or arthroplasty revision when rheumatoid disease is the underlying etiology but the operative note or diagnosis list does not specify laterality or the joint driving the RA diagnosis. Do not use M05.80 as the primary operative diagnosis for a joint-specific procedure — payers expect a site-specific code in that context. Reserve M05.80 for situations where the rheumatologist's consulting note or the problem list simply states seropositive RA without further anatomical detail and a query to the provider is not feasible or has been declined.

Excludes 1: rheumatic fever (I00), juvenile rheumatoid arthritis (M08.-), rheumatoid arthritis of the spine (M45.-). Do not combine M05.80 with those codes for the same condition. MS-DRG v43.0 groups M05.80 into DRG 545/546/547 (Connective Tissue Disorders with/without MCC/CC).

Sibling codes

Other billable codes under M05.8 (laterality / anatomic variants).

M05.89

Oth rheumatoid arthritis w rheumatoid factor mult site

M05.8A

Other rheu arthritis with rheumatoid factor of oth site

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 7 cited references ↓

01When should I use M05.80 instead of M05.9?

Use M05.80 when the provider has established that the RA falls into the 'other' seropositive subtype (i.e., it has been characterized but does not involve Felty syndrome, RA lung disease, vasculitis, myopathy, pericarditis, endocarditis, or rheumatoid nodules) and no specific joint site is documented. Use M05.9 when seropositive RA is documented but no subtype characterization has been made at all.

02Can M05.80 be used for rheumatoid arthritis affecting the spine?

No. The Excludes 1 note at the M05 category level directs you to M45.- (ankylosing spondylitis and related conditions) for spinal RA. M05.80 cannot be assigned for spinal involvement.

03Is M05.80 valid as the primary diagnosis for a total knee or hip replacement?

It is technically billable, but payers typically expect a site-specific code (e.g., M05.861 right knee, M05.851 right hip) as the primary operative diagnosis for a joint replacement. Using M05.80 when the note documents a specific joint risks a claim edit or medical necessity denial.

04Does M05.80 support HCC risk adjustment?

M05.80 maps to HCC category for inflammatory arthritis in CMS-HCC models. However, a site-specific M05.8x code with documented lab confirmation of RF positivity provides stronger support during risk adjustment audits. Query the provider for specificity whenever possible.

05What is the difference between M05.80 and M05.89?

Both fall under the M05.8 parent, but M05.89 specifies 'multiple sites' while M05.80 specifies 'unspecified site.' If the provider documents RA affecting several joints bilaterally or diffusely, M05.89 is more accurate. M05.80 is appropriate only when no site information at all is available.

06Can M05.80 be coded alongside organ-complication M05 codes?

Generally no — if the RA has a documented organ complication (e.g., RA lung disease M05.1x, vasculitis M05.2x), those specific subcategory codes replace M05.80 for that presentation. You would not layer M05.80 on top of a more specific M05 organ-complication code for the same condition.

07Which MS-DRGs does M05.80 group into?

Under MS-DRG v43.0, M05.80 groups into DRG 545 (Connective Tissue Disorders with MCC), DRG 546 (with CC), or DRG 547 (without CC/MCC), depending on the patient's complication and comorbidity profile.

Sources & references

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

Mira AI Scribe

Mira's AI scribe captures RF and anti-CCP lab values, any named joint involvement with laterality, organ-system complications (lung, heart, vasculature, nodules), and current DMARD or biologic therapy from the encounter note. That detail allows the coder to assign a site-specific M05.8x code rather than defaulting to M05.80, preventing a laterality audit flag and protecting HCC risk-adjustment accuracy.

See how Mira captures M05.80 documentation