M46.1 classifies inflammation of the sacroiliac joint(s) that does not fit under any other specific ICD-10-CM category, including presentations tied to degenerative joint disease of the SI joint.
Verified May 8, 2026 · 6 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 5
- Region
- Spine
Documentation tips
What should appear in the chart to support M46.1.
Source · Editorial brief grounded in 6 cited references ↓
- Specify laterality in the note (right, left, or bilateral) even though M46.1 has no sub-character for it — payers and auditors expect it.
- When imaging supports the diagnosis, link MRI or CT findings (subchondral sclerosis, erosions, joint space narrowing) directly to the encounter note.
- For DJD/OA of the SI joint, document the degenerative nature explicitly; AHA Coding Clinic 2Q 2020 supports M46.1, but the rationale must be traceable in the record.
- If a diagnostic or therapeutic SI joint injection is performed with image guidance, document the imaging modality (fluoroscopy or CT) used — required to support CPT 27096.
- Record prior conservative treatment history (physical therapy, NSAIDs, diagnostic blocks) to justify interventional procedures billed alongside M46.1.
Related CPT procedures
Procedure codes commonly billed with M46.1. 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 M46.1 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Using M53.3 (Sacrococcygeal disorders) when the pathology is at the sacroiliac joint, not the sacrococcygeal joint — these are anatomically distinct structures with separate codes.
- Assuming M46.1 requires imaging confirmation before use; sacroiliitis can be a clinical diagnosis, and AHA Coding Clinic supports M46.1 for DJD of the SI joint even without radiographic sacroiliitis.
- Assigning a lumbar spine code (e.g., M47.816) when the provider explicitly documents SI joint pathology — the SI joint falls under M46, not the lumbar spondylosis range.
- Failing to apply M46.1 for SI joint DJD/OA because the index routes to 'Osteoarthritis' with no SI-specific sub-entry — per AHA Coding Clinic 2Q 2020, M46.1 is the correct assignment.
- Pairing CPT 27096 (image-guided SI joint injection) without documenting the imaging modality, which can trigger a denial even when M46.1 is correctly assigned.
Clinical context
Source · Editorial summary grounded in 6 cited references ↓
M46.1 is the single billable code for sacroiliitis when the condition is not captured by a more specific inflammatory spondylopathy code. It covers unilateral (right or left) and bilateral sacroiliac joint inflammation. Note that M46.1 carries no laterality sub-characters — the code is the same regardless of sidedness. Document laterality in the clinical note for clarity, but no additional digit is available to express it in the code itself.
A critical and often overlooked application: per AHA Coding Clinic 2Q 2020, M46.1 is also the correct assignment for degenerative joint disease (DJD) or osteoarthritis of the sacroiliac joint. ICD-10-CM has no dedicated OA code for the SI joint; the index directs coders to 'Osteoarthritis,' which yields no SI-specific entry. M46.1 is the closest available alternative and is officially endorsed for this use.
Do not default to M53.3 (Sacrococcygeal disorders, not elsewhere classified) simply because imaging is unavailable or the diagnosis is framed as 'SI joint pain.' M46.1 is appropriate when the provider documents sacroiliitis — whether confirmed on imaging or by clinical diagnosis — and the sacrococcygeal structure is not involved. M53.3 addresses the sacrococcygeal joint specifically; it is a distinct anatomical structure from the sacroiliac joint.
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 6 cited references ↓
01Does M46.1 require imaging to code correctly?
02When should I use M53.3 instead of M46.1?
03Can I use M46.1 for osteoarthritis or DJD of the sacroiliac joint?
04Does M46.1 have laterality sub-characters?
05Which CPT code supports an image-guided sacroiliac joint injection under M46.1?
06What MS-DRGs does M46.1 map to for inpatient billing?
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)
- 02AHA Coding Clinic, Second Quarter 2020, p. 14 — DJD of the Sacroiliac Joint, M46.1
- 03icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M45-M49/M46-/M46.1
- 04aapc.comhttps://www.aapc.com/codes/icd-10-codes/M46.1
- 05aapc.comhttps://www.aapc.com/discuss/threads/si-joint-injection-dx-code-m46-1-vs-m53-3.185659/
- 06cms.govhttps://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=59246
Mira AI Scribe
Mira's AI scribe captures the affected side (right, left, or bilateral), provider's diagnostic statement (sacroiliitis vs. SI joint DJD vs. SI joint pain), imaging findings if referenced (MRI/CT with sclerosis, erosions, or joint space narrowing), and any prior treatment history. That documentation prevents a downcode to M53.3, supports medical necessity for image-guided injections billed under CPT 27096, and creates an audit-ready link between the clinical note and the AHA Coding Clinic 2Q 2020 rationale for DJD cases.
See how Mira captures M46.1 documentation