Adult osteochondrosis of the spine localized to the sacral and sacrococcygeal region — degenerative bone and cartilage changes at the sacrum and coccyx in a skeletally mature patient.
Verified May 8, 2026 · 4 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 9
- Region
- Spine
Documentation tips
What should appear in the chart to support M42.18.
Source · Editorial brief grounded in 4 cited references ↓
- Provider must explicitly document the region as sacral, sacrococcygeal, or coccyx — vague 'low back' language defaults to lumbar codes, not M42.18.
- Include imaging findings that support osteochondrosis: MRI signal changes at sacral endplates, CT sclerosis, or plain-film structural changes at the sacrococcygeal joint.
- Specify adult or mature skeletal status in the record to distinguish from juvenile osteochondrosis (M42.08) — age alone in the header is insufficient if the note doesn't reflect the diagnosis.
- If degeneration spans additional spinal regions, document each region involved so a coder can determine whether M42.19 (multiple sites) or individual site codes are more accurate.
- Document the clinical basis for the diagnosis — symptom correlation (coccydynia, sacral pain) plus objective findings — to support medical necessity for any associated imaging, injection, or procedural CPTs.
Related CPT procedures
Procedure codes commonly billed with M42.18. 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 M42.18 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M42.18 for a juvenile patient: skeletally immature patients with sacral osteochondrosis require M42.08, not M42.18.
- Defaulting to M42.10 (site unspecified) when the provider has clearly documented sacral or sacrococcygeal involvement — read the imaging report and the assessment before dropping to unspecified.
- Confusing sacral osteochondrosis with sacroiliac joint degeneration or sacroiliitis (M46.1x, M47.818) — these are distinct diagnoses requiring separate codes; do not substitute M42.18.
- Using M42.18 when the note documents lumbar spine disease that extends to the lumbosacral junction — that maps to M42.17 (lumbosacral region), not M42.18.
- Failing to code associated conditions (e.g., coccydynia M53.3) separately when both are documented and clinically relevant.
Clinical context
Source · Editorial summary grounded in 4 cited references ↓
M42.18 captures adult-onset spinal osteochondrosis specifically at the sacral and sacrococcygeal level. Use it when the provider documents degeneration, structural change, or osteochondrosis of the sacrum or coccyx in an adult patient — not juvenile onset (that maps to M42.08). The distinction between adult and juvenile forms is essential: if the patient is a skeletally mature adult, M42.1x is the correct parent; if documentation is silent on age group and the patient is clearly an adult, M42.18 is appropriate over the unspecified M42.9.
This code sits within the deforming dorsopathies section (M40–M43) alongside other spinal osteochondrosis codes. When disease involves more than the sacral/sacrococcygeal region, consider M42.19 (multiple sites in spine) instead. If the exact spinal region is not documented, drop to M42.10 (site unspecified). Never assign M42.18 for a juvenile patient — that requires M42.08.
Common clinical presentations driving this code include coccydynia with imaging evidence of sacrococcygeal degeneration, post-traumatic or idiopathic sacral osteochondrosis confirmed on MRI or CT, and lower pelvic axial pain workups that identify sacral endplate or cartilage changes. Imaging documentation (MRI signal changes, CT sclerosis, plain-film findings) strengthens the code assignment and supports medical necessity for associated procedures.
Sibling codes
Other billable codes under M42.1 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 4 cited references ↓
01What is the difference between M42.18 and M42.08?
02Can I use M42.18 when the degeneration spans multiple spinal levels?
03Is imaging required to assign M42.18?
04Can M42.18 be coded alongside M53.3 (coccydynia)?
05What is the parent code for M42.18, and when would I use it instead?
06How does M42.18 differ from sacroiliitis codes?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
Mira AI Scribe
Mira AI Scribe captures the provider's explicit region documentation (sacral, sacrococcygeal, or coccyx), the patient's adult skeletal status, relevant imaging findings (MRI endplate signal, CT sclerosis, plain-film changes), and any correlated symptoms such as coccydynia or lower pelvic axial pain. This prevents a drop to unspecified M42.10 or a misassignment to the juvenile code M42.08, both of which can trigger payer scrutiny or downcoding on associated procedure claims.
See how Mira captures M42.18 documentation