M86.631
BillableOther chronic osteomyelitis, right radius and ulna
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.631 an HCC code?
Yes. M86.631 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 M86.631
For M86.631 to 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 M86.631 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.631 is the ICD-10-CM diagnosis code for other chronic osteomyelitis, right radius and ulna. A chronic bone infection in the right forearm bones (radius and ulna) that has persisted over time with ongoing bone inflammation. M86.631 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other osteopathies (m86-m90).
Under the CMS-HCC V28 risk adjustment model, M86.631 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, M86.631 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.
Confirm documentation specifies 'right' side and involves both radius and ulna or either bone. Because M86.631 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 M86.631 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm documentation specifies 'right' side and involves both radius and ulna or either bone
- •Document whether this is a recurrent infection or a continuation of a previous osteomyelitis episode
Clinical Significance
Chronic osteomyelitis of the right radius and ulna represents a complex bone infection affecting both forearm bones, significantly impacting arm function and hand use. This condition often requires prolonged treatment and may result in permanent functional limitations, particularly affecting grip strength and fine motor activities.
Documentation Requirements
- ✓Documentation of chronic nature (>6 weeks duration or recurrent)
- ✓Specific involvement of right radius and/or ulna bones
- ✓Non-hematogenous etiology (contiguous spread or direct inoculation)
- ✓Imaging studies showing bone infection in forearm bones
- ✓Laboratory evidence of infection or inflammatory markers
- ✓Assessment of right forearm and hand function
- ✓Documentation of treatment regimen and surgical interventions
- ✓Evaluation of impact on activities requiring fine motor control
Commonly Confused Codes
- •M86.532 — Other chronic hematogenous osteomyelitis, left radius and ulna (hematogenous)
- •M86.632 — Other chronic osteomyelitis, left radius and ulna (opposite side)
- •M86.431 — Chronic osteomyelitis with draining sinus, right radius and ulna (has sinus)
- •M86.131 — Other acute osteomyelitis, right radius and ulna (acute phase)
- •S52.91XA — Unspecified fracture of right forearm (trauma-related)