ICD-10-CM · Spine

M08.1

Ankylosing spondylitis presenting in a pediatric patient — classified separately from adult-onset disease and reported without site-specific subcode extensions.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Spine

Drawn from CDCICD10DataAAPCIcdcodesUnboundmedicine

Documentation tips

What should appear in the chart to support M08.1.

Source · Editorial brief grounded in 5 cited references ↓

Document patient's age at symptom onset explicitly — 'juvenile onset' or a documented age supports M08.1 over adult M45.– codes.
Record imaging findings that support sacroiliitis or axial involvement: MRI or plain radiograph evidence of sacroiliac joint changes, Kellgren-Lawrence-equivalent grading where applicable.
If inflammatory bowel disease (Crohn's K50.– or ulcerative colitis K51.–) is present, document it and add the IBD code per the M08 category 'Code also' directive.
Note the treating specialty and any biologic or DMARD therapy in use — payers may request clinical justification tying the diagnosis to ordered procedures or medications.
Avoid generic 'spondylitis' language in the impression line; use 'juvenile ankylosing spondylitis' to map cleanly to M08.1 during coding review.

Related CPT procedures

Procedure codes commonly billed with M08.1. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

72148 $191.72

Non-contrast MRI of the lumbar spine used to evaluate disc pathology, spinal stenosis, nerve root compression, and other structural abnormalities without administration of contrast material.

72141 $190.72

MRI of the cervical spinal canal and its contents performed without contrast material.

72100 $40.42

Radiologic examination of the lumbosacral spine capturing two or three views, used to evaluate the lumbar vertebrae and sacrum for injury, degeneration, or structural abnormality.

77080 $39.41

Dual-energy X-ray absorptiometry measurement of bone mineral density at axial sites such as the hips, pelvis, or lumbar spine.

99213 $95.19

Established patient office or outpatient visit requiring 20–29 minutes of total time or low-complexity medical decision-making.

99214 $135.61

Office visit for an established patient requiring moderate-complexity medical decision making (MDM), or 30–39 minutes of total provider time on the date of service.

99215 $192.39

Highest-level office or outpatient E/M visit for an established patient, qualifying via high-complexity medical decision making or 40–54 minutes of total provider time on the date of service.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

27130 $1,162.02

Primary total hip arthroplasty replacing both the acetabular socket and proximal femoral components with prosthetic implants, with or without bone graft.

22800 $1,312.99

Posterior spinal arthrodesis for deformity correction spanning up to 6 vertebral segments, with or without application of a body cast.

Common coding pitfalls

The recurring mistakes coders make with M08.1 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Coding M45.0–M45.9 instead of M08.1 for a patient with juvenile-onset AS — these codes carry a hard Excludes1 against M08.1 and will create a code conflict.
Assuming M08.1 requires a site or laterality subcode — it has no subextensions; the five-character code is complete and billable as written.
Omitting a co-listed IBD code when Crohn's or ulcerative colitis is documented, which violates the M08 category 'Code also' instruction and can trigger audit scrutiny.
Using M08.0– (unspecified juvenile rheumatoid arthritis) when the record clearly specifies ankylosing spondylitis — these are distinct conditions with distinct codes.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M08.1 is the single billable code for juvenile ankylosing spondylitis (JAS), defined as axial spondyloarthritis with onset before adulthood. It sits under the M08 juvenile arthritis category and carries a hard Excludes1 relationship with M45.0– (ankylosing spondylitis in adults), meaning you cannot code both on the same claim. When the patient's chart documents ankylosing spondylitis and the onset or current treatment episode is clearly pediatric or juvenile, M08.1 is the correct code — not any subcategory of M45.

Unlike most codes in M08, there are no laterality or site subextensions for M08.1. The condition is inherently axial and bilateral, so no 6th-character site modifier exists. If an associated inflammatory bowel condition is driving or complicating the picture — specifically Crohn's disease (K50.–) or ulcerative colitis (K51.–) — ICD-10-CM instructs you to code that condition as well with a 'Code also' directive from the M08 category header.

For orthopedic practices seeing adolescent patients referred for sacroiliitis workup, spine deformity, or hip/peripheral joint involvement secondary to JAS, M08.1 supports procedure and imaging claims where adult AS codes would not. Confirm the patient's age at disease onset is documented in the record before using this code over M45.–.

Inclusion & exclusion notes

Per the official ICD-10-CM Tabular List.

Source · CDC ICD-10-CM Official Tabular List · 2026

Excludes 1 — never code together

ankylosing spondylitis in adults (M45.0-)

Sibling codes

Other billable codes under M08 (laterality / anatomic variants).

M08.3

Juvenile rheumatoid polyarthritis (seronegative)

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01Can I use M08.1 for an adult patient who was diagnosed with ankylosing spondylitis as a child?

The classification is based on age at onset, not current age. If the record documents juvenile onset, M08.1 is defensible; however, many practices transition to M45.– once the patient reaches adulthood. Document onset age explicitly and follow your payer's guidance — this is a genuinely ambiguous scenario where payer LCD rules may override default ICD-10-CM logic.

02Does M08.1 require a 7th character extension?

No. M08.1 is a 4-character code with no 7th-character extension requirement. It is complete and billable at the M08.1 level.

03What is the difference between M08.1 and M45.–?

M45.– codes ankylosing spondylitis in adults and includes site-specific subextensions for spinal region. M08.1 is juvenile onset only, carries no site subextensions, and has a hard Excludes1 relationship preventing simultaneous use of M45.– on the same claim.

04Should I add an IBD code when the patient also has Crohn's disease?

Yes. The M08 category header includes a 'Code also' instruction for regional enteritis (K50.–) and ulcerative colitis (K51.–). Omitting that secondary code violates official coding guidelines and can flag an audit.

05Which imaging CPT codes are typically paired with M08.1 for a sacroiliitis workup?

MRI of the sacroiliac joints without contrast (72148 for lumbar spine MRI is commonly used; a dedicated SI joint MRI may also be submitted) and plain radiographs of the spine (72100 for lumbar AP/lateral) are the most common pairings. Confirm local payer LCD requirements for medical necessity documentation.

06Is M08.1 used differently in pediatric orthopedic versus rheumatology settings?

The code itself is the same across specialties. Orthopedic encounters typically focus on structural consequences — sacroiliac fusion, hip joint involvement, or spinal deformity — while rheumatology drives the primary diagnosis. Either specialty may report M08.1; the supporting documentation requirements do not change by specialty.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

Mira Scribe

Mira AI Scribe captures the patient's age at disease onset, documented sacroiliitis or axial imaging findings (MRI or radiograph), any peripheral joint involvement, current biologic or DMARD therapy, and associated IBD diagnoses — everything needed to confirm M08.1 over an adult M45 code and satisfy a 'Code also' requirement for comorbid Crohn's or ulcerative colitis.

See how Mira captures M08.1 documentation