M05.821 ICD-10-CM Code: Other rheumatoid arthritis with rheumatoid factor of right elbow
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)
M05.821
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther rheumatoid arthritis with rheumatoid factor of right elbow
A type of rheumatoid arthritis affecting the right elbow in patients who test positive for rheumatoid factor, an antibody associated with this autoimmune joint disease.
Buddy Insight
This code captures other specified manifestations of seropositive rheumatoid arthritis with positive rheumatoid factor, representing a systemic autoimmune condition with potential for progressive joint destruction and disability.
CMS-HCC V28
MappedHCC 93
RAF 0.175
CMS-HCC V24
MappedHCC 40
RAF 0.307
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 40
RAF 0.0
RXHCC
MappedHCC 83
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M05.821 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M05.821 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M05.821 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M05.821 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M05.821 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M05.821 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M05.821 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M05.821 an HCC code?
Yes. M05.821 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for M05.821
For M05.821to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M05.821 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
M05.821 is the ICD-10-CM diagnosis code for other rheumatoid arthritis with rheumatoid factor of right elbow. A type of rheumatoid arthritis affecting the right elbow in patients who test positive for rheumatoid factor, an antibody associated with this autoimmune joint disease. M05.821 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering inflammatory polyarthropathies (m05-m14).
Under the CMS-HCC V28 risk adjustment model, M05.821 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 93) with a community, non-dual, aged base RAF weight of 0.175. Under the older V24 model, M05.821 mapped to the same category but with a base RAF weight of 0.307, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Verify the laterality (right side) is documented in the medical record before assigning this code. Because M05.821 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M05.821 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the laterality (right side) is documented in the medical record before assigning this code
- •Confirm rheumatoid factor positivity is documented; if factor status is unknown or negative, use a different M05 code
Clinical Significance
This code captures other specified manifestations of seropositive rheumatoid arthritis with positive rheumatoid factor, representing a systemic autoimmune condition with potential for progressive joint destruction and disability. Accurate capture is essential for risk adjustment as it reflects significant ongoing treatment burden including disease-modifying antirheumatic drugs, biologics, and regular laboratory monitoring.
Documentation Requirements
- ✓Clinical diagnosis of rheumatoid arthritis clearly documented by the treating provider
- ✓Rheumatoid factor lab result status (positive or negative) consistent with the code selected
- ✓Affected joint(s) specified with laterality (right, left, or bilateral)
- ✓Current disease status: active, in remission, or chronic stable
- ✓Current treatment plan including medications (disease-modifying antirheumatic drugs, biologics, nonsteroidal anti-inflammatory drugs)
- ✓Specification of the 'other' rheumatoid arthritis manifestation or feature that distinguishes it from standard presentations
- ✓Assessment and plan addressing rheumatoid arthritis at each encounter where it impacts care or treatment
Commonly Confused Codes
- •M05.7xx (Rheumatoid arthritis with rheumatoid factor without organ involvement, same site): Use M05.7xx for the standard seropositive presentation without organ or systems involvement
- •M06.0xx (Rheumatoid arthritis without rheumatoid factor, same site): Use M06.0xx when rheumatoid factor is negative
- •M06.9 (Rheumatoid arthritis, unspecified): A nonspecific code that does not indicate rheumatoid factor status; avoid when rheumatoid factor status is known
- •M05.0x-M05.6x (Rheumatoid arthritis with organ involvement such as Felty syndrome, rheumatoid lung, vasculitis): Use these when extra-articular manifestations are documented
- •M19.x (Osteoarthritis): Osteoarthritis is a degenerative, non-autoimmune condition; do not confuse with rheumatoid arthritis which is inflammatory and autoimmune