M66.33 — Spontaneous rupture of flexor tendons, forearm

Not billable

Is M66.33 billable?

No — M66.33 is a non-billable header code. M66.33 groups more specific codes and cannot be submitted on a claim. A valid ICD-10-CM code must be reported at the highest level of specificity available in its branch. Select one of the 3 billable codes beneath M66.33.

Billable codes under this header

M66.33 at a glance

Code	M66.33
Description	Spontaneous rupture of flexor tendons, forearm
Billable	No — header code
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

How is M66.33 listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to M66.33. They show the wording a clinician may have documented, which often differs from the Tabular description.

Rupture, ruptured › tendon › nontraumatic › flexor › forearm

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M66.33, but a patient may have both at the same time. When documentation supports it, M66.33 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)

Excludes2 — not included here — inherited from M66

The conditions below are not part of M66.33, but a patient may have both at the same time. When documentation supports it, M66.33 and the excluded code may both be reported.

rotator cuff syndrome (M75.1-)
rupture where an abnormal force is applied to normal tissue - see injury of tendon by body region

What codes fall under M66.33? (3)

How long has M66.33 existed?

M66.33 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.

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