M65.99 — Unspecified synovitis and tenosynovitis, multiple sites

BillableUnspecified

Is M65.99 billable?

Yes, but M65.99 is an unspecified code. M65.99 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, M65.99 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting M65.99 — the more specific alternatives are listed below.

More specific alternatives

M65.99 at a glance

Code	M65.99
Description	Unspecified synovitis and tenosynovitis, multiple sites
Billable	Yes
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

Which MS-DRGs does M65.99 group to?

M65.99 sits in MDC 08 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.

557Tendonitis, Myositis and Bursitis with MCCmedical
558Tendonitis, Myositis and Bursitis without MCCmedical

How is M65.99 listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to M65.99. They show the wording a clinician may have documented, which often differs from the Tabular description.

Synovitis › multiple sites, unspecified type

Excludes1 — never code together — inherited from M65

The conditions below can never be reported together with M65.99 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.

chronic crepitant synovitis of hand and wrist (M70.0-)
current injury - see injury of ligament or tendon by body region
soft tissue disorders related to use, overuse and pressure (M70.-)

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M65.99, but a patient may have both at the same time. When documentation supports it, M65.99 and the excluded code may both be reported.

arthropathic psoriasis (L40.5-)
certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
compartment syndrome (traumatic) (T79.A-)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

How long has M65.99 existed?

M65.99 first appears in FY2025.

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.

Which conditions are coded to M65.99?

ICD-10 code for Synovitis