M86.459
BillableChronic osteomyelitis with draining sinus, unspecified femur
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.459 an HCC code?
Yes. M86.459 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 M86.459
For M86.459 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 M86.459 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.459 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, unspecified femur. A chronic bone infection of the thighbone (femur) with an unspecified side that has created an open drainage channel through the skin, allowing infected material to drain continuously. M86.459 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, M86.459 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, M86.459 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.
Use this code only when the medical record does not specify right or left femur. Because M86.459 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 M86.459 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when the medical record does not specify right or left femur
- •Query the provider if laterality can be determined from imaging or clinical documentation to assign a more specific code
Clinical Significance
Chronic osteomyelitis with draining sinus of the unspecified femur represents a severe, complicated bone infection with persistent external drainage pathway. This condition indicates advanced osteomyelitis requiring aggressive treatment including prolonged antibiotics, surgical debridement, and management of the draining sinus tract, significantly impacting patient mobility and quality of life.
Documentation Requirements
- ✓Documentation of chronic osteomyelitis diagnosis
- ✓Clear evidence of draining sinus tract presence
- ✓Femur involvement specified but laterality unspecified
- ✓Description of sinus tract characteristics and drainage
- ✓Microbiological studies from drainage or bone
- ✓Imaging studies confirming osteomyelitis and sinus tract
- ✓Treatment history including antibiotic therapy duration
- ✓Surgical interventions and wound management documentation
Commonly Confused Codes
- •M86.451 — Chronic osteomyelitis with draining sinus, right femur (has laterality)
- •M86.452 — Chronic osteomyelitis with draining sinus, left femur (has laterality)
- •M86.659 — Other chronic osteomyelitis, unspecified femur (no draining sinus)
- •M86.559 — Other chronic hematogenous osteomyelitis, unspecified femur (different type, no sinus)