ICD-10-CM · Other

M06.8A

Other specified rheumatoid arthritis affecting a site that does not map to any of the named anatomical locations in the M06.8 subcategory — used when the involved joint or structure is documented but falls outside shoulder, elbow, wrist, hand, hip, knee, ankle/foot, vertebrae, or multiple sites.

Verified May 8, 2026 · 6 sources ↓

Status: Billable
Chapter: 13
Related CPT: 5
Region: Other

Drawn from CDCICD10DataAAPCUnboundmedicineRheumatologyadvisor

Documentation tips

What should appear in the chart to support M06.8A.

Source · Editorial brief grounded in 6 cited references ↓

Explicitly name the affected joint or anatomical structure — 'TMJ' or 'sternoclavicular joint,' for example — so reviewers can confirm no site-specific M06.8x code exists for that location.
Document rheumatoid factor (RF) and anti-CCP serology results; a positive RF may redirect coding to a seropositive M05 code rather than M06.8A.
Record the RA variant or subtype (e.g., seronegative, overlap syndrome, other specified form) that justifies the 'other specified' designation over M06.9.
If interstitial lung disease is present, document the RA as the underlying condition so the coder can apply the required 'Code first' sequencing with J84.17x.
Include disease activity level or clinical scoring (e.g., CDAI, DAS28) and current DMARD or biologic therapy — supports medical necessity for advanced treatments and audits.

Related CPT procedures

Procedure codes commonly billed with M06.8A. Linking the right diagnosis to the right procedure is what establishes medical necessity.

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

20610 $68.81

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

20600 $56.11

Needle aspiration and/or injection of a small joint or bursa — such as a finger or toe joint — performed without ultrasound guidance.

21480 $172.01

Closed manual reduction of a temporomandibular joint dislocation, initial or subsequent encounter.

21485 $1,001.69

Closed treatment of a complicated temporomandibular joint dislocation — including recurrent cases requiring intermaxillary fixation or splinting — reported for initial or subsequent encounters.

97110 $29.06

Therapeutic exercise billed per 15-minute unit, targeting strength, endurance, range of motion, or flexibility with direct one-on-one patient contact.

Common coding pitfalls

The recurring mistakes coders make with M06.8A and adjacent codes.

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

Using M06.8A when a named site-specific code exists: if the joint is shoulder, elbow, wrist, hand, hip, knee, ankle/foot, or vertebrae, the correct code is M06.81–M06.88, not M06.8A.
Defaulting to M06.9 (unspecified) when the provider has named both the RA type and the affected site — M06.8A is the billable, specific code that payers expect when documentation supports it.
Ignoring serology: a seropositive patient with RA at an 'other specified' site should be evaluated against M05 codes before assigning M06.8A, which lives under M06 (Other rheumatoid arthritis, generally seronegative or unspecified serology).
Failing to sequence correctly when RA-associated interstitial lung disease is present — M06.8A must be coded as secondary after the J84.17x lung disease code per Tabular List instructions.
Conflating M06.8A with M06.89 (multiple sites): M06.8A is for a single, documentable site that has no dedicated subcategory code; M06.89 applies when multiple distinct sites are involved.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

M06.8A captures other specified rheumatoid arthritis at an anatomical site that has no dedicated code within the M06.8 series. The prime real-world use case is temporomandibular joint (TMJ) involvement in RA — the code was added in FY2021 specifically to accommodate joints like the TMJ that lacked a site-specific home elsewhere in the subcategory. If the affected site is the shoulder, elbow, wrist, hand, hip, knee, ankle/foot, or vertebrae, those site-specific codes (M06.81–M06.88) apply instead.

M06.8A sits under parent M06.8 (Other specified rheumatoid arthritis), which itself sits under M06 (Other rheumatoid arthritis). 'Other specified' in this context means the RA type does not fall under seropositive RA (M05), seronegative RA (M06.0), adult-onset Still's disease (M06.1), rheumatoid bursitis (M06.2), rheumatoid nodule (M06.3), or inflammatory polyarthropathy (M06.4). Document the specific RA variant and the exact joint or structure involved to justify M06.8A over the unspecified fallback M06.80 or the catch-all M06.9.

When RA causes interstitial lung disease, code the lung condition first (e.g., J84.170 or J84.178) with M06.8A as a secondary code per the 'Code first underlying disease' instruction in the Tabular List. Confirm serology status in the chart: if the patient is seropositive, evaluate whether an M05 code is more precise before landing on M06.8A.

Sibling codes

Other billable codes under M06.8 (laterality / anatomic variants).

M06.80

Other specified rheumatoid arthritis, unspecified site

M06.88

Other specified rheumatoid arthritis, vertebrae

M06.89

Other specified rheumatoid arthritis, multiple sites

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 6 cited references ↓

01When was M06.8A added to ICD-10-CM?

M06.8A became effective October 1, 2020 (FY2021), proposed at the March 2019 ICD-10 Coordination and Maintenance Committee meeting specifically to accommodate joints such as the TMJ that had no site-specific code in the M06.8 series.

02Is M06.8A appropriate for temporomandibular joint RA?

Yes. The TMJ is the primary real-world use case for M06.8A. The TMJ does not have a dedicated code under M06.81–M06.88, so when RA involves the TMJ and is documented as 'other specified,' M06.8A is the correct billable code.

03What is the difference between M06.8A and M06.80?

M06.80 is used when the site is unspecified — the provider has not documented which joint is involved. M06.8A requires that a specific site be documented; it just happens to be a site outside the named locations in M06.81–M06.88.

04Can M06.8A be used for a seropositive RA patient?

Only if no M05 code fits the clinical picture. M06.8A sits under M06 (Other rheumatoid arthritis), which generally applies when seropositive RA codes (M05) are not appropriate. Review RF and anti-CCP results and the specific RA variant before choosing M06.8A over an M05 code.

05How should M06.8A be sequenced when the patient also has RA-associated interstitial lung disease?

Code the interstitial lung disease first (e.g., J84.170 or J84.178) per the Tabular List 'Code first underlying disease' instruction, then list M06.8A as a secondary diagnosis to identify RA as the underlying condition.

06Should I use M06.8A or M06.89 when multiple atypical joints are affected?

Use M06.89 (multiple sites) when RA involves several joints simultaneously. M06.8A is reserved for a single site that falls outside the named locations in M06.81–M06.88. If one of those multiple sites is the TMJ plus a named site, clinical judgment and query may be needed to determine the principal site or whether M06.89 better captures the encounter.

Sources & references

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

Mira AI Scribe

Mira AI Scribe captures the specific joint name (e.g., temporomandibular, sternoclavicular), RF and anti-CCP lab values, current biologic or DMARD regimen, and any imaging or clinical findings confirming inflammatory arthropathy at that site. That documentation prevents a downcode to M06.9 (unspecified) and closes the audit gap that arises when 'other specified' is claimed without an identified site.

See how Mira captures M06.8A documentation