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M05.161 ICD-10-CM Code: Rheumatoid lung disease with rheumatoid arthritis of right knee

Compare with another code for M05.161Check this code on a claim

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
3 Excludes1
Risk adjustment
CMS-HCC V28: 1 category · CMS-HCC V22 category 40 · RxHCC V08 category 83

Billable · FY2027A valid, specific ICD-10-CM code, reportable for dates of service in FY2027.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

Excludes1from M05Not reported with this code unless documented as unrelated
  • rheumatic fever (I00)
  • juvenile rheumatoid arthritis (M08.-)
  • rheumatoid arthritis of spine (M45.-)

Where it sits Source: CMS/NCHS

Under:Chapter 13: Diseases of the Musculoskeletal System and Connective TissueM00-M25 ArthropathiesM05-M14 Inflammatory polyarthropathiesM05 Rheumatoid arthritis with rheumatoid factorM05.1 Rheumatoid lung disease with rheumatoid arthritisM05.16 Rheumatoid lung disease with rheumatoid arthritis of knee

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related Codes

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v44, Appendix B.

  • MS-DRG 196 — INTERSTITIAL LUNG DISEASE WITH MCC (MDC 04)
  • MS-DRG 197 — INTERSTITIAL LUNG DISEASE WITH CC (MDC 04)
  • MS-DRG 198 — INTERSTITIAL LUNG DISEASE WITHOUT CC/MCC (MDC 04)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (supersedes HCC 94)

Other models: CMS-HCC V22 HCC 40 · RxHCC V08 HCC 83

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for M05.161 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

Notes without a marker are published on M05.161 itself; “inherited from” names the category or block whose note applies here.

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from M05

Coder workflow for M05.161

MedCoder structured workflow — derived from this code’s own official record

Before you code M05.161

  1. Laterality is coded in this family. Confirm the side documented — right, left, or bilateral — and select the matching code (this page’s code: right). The unspecified-side code applies only when the record states no side. Laterality is assigned from the documented side; where a bilateral code exists and both sides are documented, it is used instead of two unilateral codes (Guidelines I.B.13).

    ReviewM05.162 · left, M05.169 · unspecified

    Guide: Laterality coding →

  2. M05.161’s title joins a condition with an associated condition or complication. Confirm each component is documented. Where the classification presumes the link through the “with” convention, only a provider statement that the conditions are unrelated defeats it. A combination code is assigned only when it fully identifies the documented conditions; a required second code for the stage, type or manifestation is still reported when the notes ask for it (Guidelines I.B.9, I.A.15).

    Guide: Combination codes →

  3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with M05.161. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in M05.161’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewI00, M08, M45

  2. Is the side documented?
    Yes → Select the code for the documented side (or the bilateral code when both sides are documented and one exists).
    No → Use the unspecified-side code only when the record states no side; a query is the alternative.

    ReviewM05.162 · left, M05.169 · unspecified

Consider M05.161. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
Laterality
Right, left or bilateral as documented; unspecified only when the record states no side (Guidelines I.B.13).
The associated condition or complication
Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).

Official instructions as workflow

  • Excludes1 — check before selecting M05.161(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with M05.161: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareI00, M08, M45

    See the official tabular notes · Guidelines I.A.12.a

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition M05.161 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewI00, M08, M45

Documentation: The record documents the condition on one side only.

Coding question: Which code in this family applies?

Path: Select the sibling code for the documented side.

Reason: Laterality is assigned from the documented side; the unspecified-side code is for records that state no side (Guidelines I.B.13).

ReviewM05.162 · left, M05.169 · unspecified

Documentation: Only one of the components this code’s title joins is documented.

Coding question: Is M05.161 supported?

Path: Review the code for the documented component on its own.

Reason: A combination code is assigned only when it fully identifies the documented conditions; otherwise the documented component takes its own code (Guidelines I.B.9).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse M05.161 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of M05.161 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • I00— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of rheumatic fever moves the case to I00; the two are not reported together unless documented as unrelated.

    Full comparison: M05.161 vs I00 →

  • M08— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of juvenile rheumatoid arthritis moves the case to M08; the two are not reported together unless documented as unrelated.

    Full comparison: M05.161 vs M08 →

  • M45— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of rheumatoid arthritis of spine moves the case to M45; the two are not reported together unless documented as unrelated.

    Full comparison: M05.161 vs M45 →

  • M05.169— Specificity relationship (Review)

    Overlapping diagnoses in the same category.

    Overlapping codes in the same category — the documentation decides which is the more specific fit.

    What moves you there: A record that documents no more than “Rheumatoid lung disease with rheumatoid arthritis of unspecified knee” takes M05.169; specificity in the record moves it back here.

    Full comparison: M05.161 vs M05.169 →

  • M05.162— Laterality relationship (Review)

    Same condition; these differ only in which side is documented.

    The same condition with a different side named (the opposite side, both sides, or none); the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

    What moves you there: A documented left side moves the case to M05.162.

    Full comparison: M05.161 vs M05.162 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

Code Overview

Rheumatoid lung disease with rheumatoid arthritis of right knee is a billable ICD-10-CM diagnosis code (M05.161).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder-derived relationships — computed from published CMS and AHRQ datasets

Other codes that name M05.161 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: R76.81 — Abnormal rheumatoid factor and anti-citrullinated protein antibody without rheumatoid arthritis (via M05.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 2 Code First instructions: J84.170 — Interstitial lung disease with progressive fibrotic phenotype in diseases classified elsewhere (via M05.-), J84.178 — Other interstitial pulmonary diseases with fibrosis in diseases classified elsewhere (via M05.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Referenced by 1 Code Also instruction: I27.21 — Secondary pulmonary arterial hypertension (via M05.-).

These codes suggest coding this condition alongside when both are present.

MS-DRG Grouper Relationships (FY2027)

Potential MS-DRG participation — not a DRG assignment.

FY2027 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 196 (MDC 04), DRG 197 (MDC 04), DRG 198 (MDC 04).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):MUS003 — Rheumatoid arthritis and related disease (default); RSP016 — Other specified and unspecified lower respiratory disease.

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same condition, different side

Same title, differing only in which side of the body it names: right, left, bilateral or unspecified.

M05.162 — Rheumatoid lung disease with rheumatoid arthritis of left knee (left)Compare M05.161 vs M05.162 →, M05.169 — Rheumatoid lung disease with rheumatoid arthritis of unspecified knee (unspecified)Compare M05.161 vs M05.169 →

Same CMS-HCC risk category (V28)

CMS maps these diagnoses to the same Hierarchical Condition Category (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders) for risk-adjusted payment.

M05.129 — Rheumatoid lung disease with rheumatoid arthritis of unspecified elbow, M05.131 — Rheumatoid lung disease with rheumatoid arthritis of right wrist, M05.132 — Rheumatoid lung disease with rheumatoid arthritis of left wrist, M05.139 — Rheumatoid lung disease with rheumatoid arthritis of unspecified wrist, M05.141 — Rheumatoid lung disease with rheumatoid arthritis of right hand, M05.142 — Rheumatoid lung disease with rheumatoid arthritis of left hand, M05.149 — Rheumatoid lung disease with rheumatoid arthritis of unspecified hand, M05.151 — Rheumatoid lung disease with rheumatoid arthritis of right hip, M05.152 — Rheumatoid lung disease with rheumatoid arthritis of left hip, M05.159 — Rheumatoid lung disease with rheumatoid arthritis of unspecified hip, M05.162 — Rheumatoid lung disease with rheumatoid arthritis of left knee, M05.169 — Rheumatoid lung disease with rheumatoid arthritis of unspecified knee, M05.171 — Rheumatoid lung disease with rheumatoid arthritis of right ankle and foot, M05.172 — Rheumatoid lung disease with rheumatoid arthritis of left ankle and foot, M05.179 — Rheumatoid lung disease with rheumatoid arthritis of unspecified ankle and foot, M05.19 — Rheumatoid lung disease with rheumatoid arthritis of multiple sites, M05.20 — Rheumatoid vasculitis with rheumatoid arthritis of unspecified site, M05.211 — Rheumatoid vasculitis with rheumatoid arthritis of right shoulder, M05.212 — Rheumatoid vasculitis with rheumatoid arthritis of left shoulder, M05.219 — Rheumatoid vasculitis with rheumatoid arthritis of unspecified shoulder, +487 more

Related risk categories

These categories interact through CMS's HCC hierarchy — one can suppress the other's risk-adjustment weight when both are present on a claim.

Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical categories (Rheumatoid arthritis and related disease, Other specified and unspecified lower respiratory disease).

M05.112 — Rheumatoid lung disease with rheumatoid arthritis of left shoulder, M05.119 — Rheumatoid lung disease with rheumatoid arthritis of unspecified shoulder, M05.121 — Rheumatoid lung disease with rheumatoid arthritis of right elbow, M05.122 — Rheumatoid lung disease with rheumatoid arthritis of left elbow, M05.129 — Rheumatoid lung disease with rheumatoid arthritis of unspecified elbow, M05.131 — Rheumatoid lung disease with rheumatoid arthritis of right wrist, M05.132 — Rheumatoid lung disease with rheumatoid arthritis of left wrist, M05.139 — Rheumatoid lung disease with rheumatoid arthritis of unspecified wrist, M05.141 — Rheumatoid lung disease with rheumatoid arthritis of right hand, M05.142 — Rheumatoid lung disease with rheumatoid arthritis of left hand, M05.149 — Rheumatoid lung disease with rheumatoid arthritis of unspecified hand, M05.151 — Rheumatoid lung disease with rheumatoid arthritis of right hip, M05.152 — Rheumatoid lung disease with rheumatoid arthritis of left hip, M05.159 — Rheumatoid lung disease with rheumatoid arthritis of unspecified hip, M05.162 — Rheumatoid lung disease with rheumatoid arthritis of left knee, M05.169 — Rheumatoid lung disease with rheumatoid arthritis of unspecified knee, M05.171 — Rheumatoid lung disease with rheumatoid arthritis of right ankle and foot, M05.172 — Rheumatoid lung disease with rheumatoid arthritis of left ankle and foot, M05.179 — Rheumatoid lung disease with rheumatoid arthritis of unspecified ankle and foot, M05.19 — Rheumatoid lung disease with rheumatoid arthritis of multiple sites, +377 more

Contextual Map

Every relationship of M05.161 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run M05.161 with these 4 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code First instructions

Referenced by Code Also instructions

Clinical classification (CCSR)

Risk adjustment (CMS-HCC)

  • HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders [CMS-HCC]: “Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders — supersedes HCC 94 (Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders)”— CMS-HCC V28 · 2026

MS-DRG Grouper

MDC crossing

  • MDC 04 — Diseases and Disorders of the Respiratory System[MDC crossing]: “Diseases and Disorders of the Respiratory System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 4,000 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2027

Nearest codes (40)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v44 Release, file and checksum · Publisher’s page
Risk adjustment Official source data
2026 Mid-Year Final ICD-10 Mappings + Model Software (cms.gov/files/zip/2026-midyear-final-icd-10-mappings.zip, 2026-midyear-final-model-software.zip) — CMS-HCC V28, PY2026 mid-year final release Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder-derived relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder editorial explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "M05.161 — Rheumatoid lung disease with rheumatoid arthritis of right knee." ICD-10-CM FY2027. https://medcoder.ai/icd10/code/m05.161-rheumatoid-lung-disease-with-rheumatoid-arthritis-of-right-knee

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Rheumatoid lung disease with rheumatoid arthritis of right knee

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027, and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to M05.161 in its code family, with their registry titles.

View all codes in the M05 family