M02.861
BillableOther reactive arthropathies, right knee
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M02.861 an HCC code?
Yes. M02.861 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis 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 M02.861
For M02.861to 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 M02.861 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M02.861 is the ICD-10-CM diagnosis code for other reactive arthropathies, right knee. Joint inflammation in the right knee that develops as a reaction to an infection or other trigger elsewhere in the body. M02.861 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering infectious arthropathies (m00-m02).
Under the CMS-HCC V28 risk adjustment model, M02.861 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M02.861 mapped to the same category but with a base RAF weight of 0.482 — 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.
Knee reactive arthropathy commonly follows gastrointestinal or genitourinary infections; document the trigger. Because M02.861 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 M02.861 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Knee reactive arthropathy commonly follows gastrointestinal or genitourinary infections; document the trigger
- •Note any associated symptoms such as effusion, swelling, or gait disturbance in the clinical record
Clinical Significance
This diagnosis represents reactive arthropathy affecting the right knee, indicating inflammation of this crucial weight-bearing joint secondary to a remote infectious process. Knee involvement significantly impacts mobility, ambulation, and functional independence, requiring prompt management to prevent long-term disability.
Documentation Requirements
- ✓Clinical evidence of right knee joint inflammation (swelling, pain, stiffness, effusion)
- ✓Documentation of reactive nature - inflammation secondary to remote infection
- ✓Specific anatomical location identified as right knee joint
- ✓Evidence ruling out direct septic arthritis or other infectious arthropathies
- ✓Documentation of triggering infection or infectious process (if identified)
- ✓Physical examination findings consistent with knee arthritis
- ✓Exclusion of other arthropathy types (rheumatoid, osteoarthritis, crystal arthropathy)
- ✓Assessment of functional impact on weight-bearing and mobility
Commonly Confused Codes
- •M00.062 — Staphylococcal arthritis of right knee (infectious vs reactive)
- •M06.062 — Rheumatoid arthritis of right knee (autoimmune vs reactive)
- •M17.11 — Unilateral primary osteoarthritis, right knee (degenerative vs reactive)
- •M02.862 — Other reactive arthropathies, left knee (laterality difference)
- •M25.562 — Pain in right knee (symptom vs specific arthropathy diagnosis)