M46.86 captures inflammatory spondylopathies of the lumbar spine that are confirmed but do not fit a more precisely defined category such as ankylosing spondylitis (M45) or reactive arthritis. It is a billable, site-specific code under the M46.8 'other specified' parent.
Verified May 8, 2026 · 5 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 10
- Region
- Spine
Documentation tips
What should appear in the chart to support M46.86.
Source · Editorial brief grounded in 5 cited references ↓
- Specify 'lumbar region' or name the affected vertebral levels (L1–L5) explicitly — this justifies the 6th-character site selection over unspecified or multi-site alternatives.
- Record the inflammatory basis: elevated CRP/ESR, positive HLA-B27, MRI evidence of bone marrow edema, or rheumatology consultation confirming an inflammatory rather than degenerative process.
- If the diagnosis is nr-axSpA, document the absence of radiographic sacroiliitis to distinguish it from ankylosing spondylitis (M45) and justify use of the M46.8x 'other specified' category.
- Note any prior or concurrent diagnoses (e.g., psoriatic arthritis, IBD-related spondylopathy) that could point to a more specific code; M46.86 is appropriate only when no other named inflammatory spondylopathy code fits.
- Document the treating provider's clinical reasoning for selecting an inflammatory over a mechanical or degenerative diagnosis to withstand payer audit scrutiny.
Related CPT procedures
Procedure codes commonly billed with M46.86. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M46.86 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Defaulting to M46.86 for generic low back pain without documented inflammatory findings — this is a specificity mismatch that will not hold up under audit; M54.51 (vertebrogenic low back pain) or M54.59 is more appropriate for non-inflammatory pain.
- Using M46.86 when ankylosing spondylitis with lumbar involvement is confirmed — that presentation belongs to M45.6, not M46.86.
- Selecting M46.86 when the lumbar and sacral or lumbosacral regions are both affected — M46.87 (lumbosacral) or M46.89 (multiple sites) captures the full anatomic extent.
- Confusing M46.86 with M46.96 (unspecified inflammatory spondylopathy, lumbar region) — use M46.86 only when the provider has specified that the condition is a named or characterized inflammatory spondylopathy that simply lacks its own distinct code, not when the type is entirely unknown.
- Omitting an accompanying rheumatologic or laboratory code that supports the inflammatory diagnosis, which can trigger payer requests for additional documentation.
Clinical context
Source · Editorial summary grounded in 5 cited references ↓
Use M46.86 when the provider has documented an inflammatory process affecting the lumbar spine — with supporting clinical, laboratory, or imaging evidence — but the condition does not meet criteria for a named category like ankylosing spondylitis, sacroiliitis, or pyogenic vertebral osteomyelitis. Common clinical scenarios include early or suspected axial spondyloarthritis with lumbar involvement where radiographic sacroiliitis is absent (non-radiographic axial spondyloarthritis, nr-axSpA), as well as undifferentiated inflammatory spondylopathies localized to L1–L5.
M46.86 is region-specific: the 6th character '6' designates the lumbar region. If the inflammatory process extends into the lumbosacral junction, consider M46.87 (lumbosacral region) instead. If multiple spinal regions are involved, M46.89 (multiple sites) may be more accurate. Do not use M46.86 as a catch-all for nonspecific low back pain — the documentation must substantiate an inflammatory, not mechanical or degenerative, etiology.
This code maps to MS-DRG 551 (Medical back problems with MCC) and 552 (Medical back problems without MCC) under v43.0. It has been stable in the ICD-10-CM code set since its introduction in FY2016 and remains unchanged in FY2026 (effective October 1, 2025).
Sibling codes
Other billable codes under M46.8 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 5 cited references ↓
01What is the difference between M46.86 and M45.6?
02Can M46.86 be used for non-radiographic axial spondyloarthritis (nr-axSpA)?
03When should I use M46.87 instead of M46.86?
04Is M46.86 appropriate when the provider documents 'inflammatory back pain' without a specific diagnosis?
05What MS-DRGs does M46.86 map to?
06Does M46.86 require a 7th character extension?
07Can M46.86 be reported alongside a biologic medication code or rheumatology E&M?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M45-M49/M46-/M46.86
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M46.86
- 04findacode.comhttps://www.findacode.com/articles/watch-out-for-new-icd-10-cm-codes-36885.html
- 05cms.govhttps://www.cms.gov/Medicare/Coding/ICD10/Downloads/2019-ICD10-Coding-Guidelines-.pdf
Mira AI Scribe
Mira AI Scribe captures spinal region (lumbar, L1–L5 levels), inflammatory indicators (HLA-B27 status, CRP/ESR values, MRI bone marrow edema findings), presence or absence of radiographic sacroiliitis, and any prior rheumatology evaluation. That documentation chain locks in M46.86 over the vaguer M46.96 (unspecified) and prevents downcoding or a medical-necessity denial from payers demanding evidence of an inflammatory — not degenerative — process.
See how Mira captures M46.86 documentation