M05.742
BillableRheumatoid arthritis with rheumatoid factor of left hand without organ or systems involvement
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M05.742 an HCC code?
Yes. M05.742 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 M05.742
For M05.742to 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 M05.742 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M05.742 is the ICD-10-CM diagnosis code for rheumatoid arthritis with rheumatoid factor of left hand without organ or systems involvement. Rheumatoid arthritis affecting the left hand with a positive rheumatoid factor blood test, without involvement of other organs or body systems. M05.742 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, M05.742 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, M05.742 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.
Confirm left hand is documented in the clinical record before assignment. Because M05.742 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 M05.742 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm left hand is documented in the clinical record before assignment
- •Hand involvement typically includes finger joints and metacarpophalangeal joints
Clinical Significance
This diagnosis represents seropositive rheumatoid arthritis affecting the left hand without systemic involvement, indicating localized inflammatory arthritis with confirmed positive rheumatoid factor. Hand arthritis severely impacts daily functioning and quality of life, requiring ongoing specialized care despite absence of systemic disease.
Documentation Requirements
- ✓Confirmation of rheumatoid arthritis diagnosis in left hand joints
- ✓Positive rheumatoid factor laboratory result documented
- ✓Confirmation that no organ or system involvement exists
- ✓Clinical evidence of inflammatory arthritis specifically in left hand
- ✓Exclusion of extra-articular manifestations
- ✓Documentation of disease activity and functional limitation assessment
- ✓Clear identification of left hand laterality
Commonly Confused Codes
- •M05742 vs M05741 — Wrong laterality (right vs left hand)
- •M05742 vs M19.042 — M19.042 is primary osteoarthritis of left hand
- •M05742 vs M25.542 — M25.542 is pain in left hand without inflammation
- •M05742 vs M65.842 — M65.842 is tenosynovitis of left hand
- •M05742 vs M05.642 — M05.642 includes systemic organ involvement