M66.1 – Rupture of synovium

ICD-10-CM 2027 diagnosis code · Disorders of synovium and tendon

Non-billable header

ICD-10-CM code M66.1

Code: M66.1 (claims format: M661)
Description: Rupture of synovium
Billable: No – use a more specific code below
Valid for: Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter: 13. Diseases of the musculoskeletal system and connective tissue (M00-M99)
Block: M65-M67 Disorders of synovium and tendon
Parent codes: M66

Billable codes under M66.1

M66.1 is a header code and cannot be used on claims. Choose the most specific code:

M66.10 – Rupture of synovium, unspecified jointBillable
M66.11 – Rupture of synovium, shoulderHeader (more codes below)
M66.12 – Rupture of synovium, elbowHeader (more codes below)
M66.13 – Rupture of synovium, wristHeader (more codes below)
M66.14 – Rupture of synovium, hand and fingersHeader (more codes below)
M66.15 – Rupture of synovium, hipHeader (more codes below)
M66.17 – Rupture of synovium, ankle, foot and toesHeader (more codes below)
M66.18 – Rupture of synovium, other siteBillable

Notes for M66.1

Applicable to:

Rupture of synovial cyst

Excludes2 (not included here):

rupture of popliteal cyst (M66.0)

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

M66 – Spontaneous rupture of synovium and tendon

Includes:

rupture that occurs when a normal force is applied to tissues that are inferred to have less than normal strength

Excludes2 (not included here):

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

Related codes in M66

Frequently asked questions

What is ICD-10 code M66.1?

M66.1 is the ICD-10-CM code for rupture of synovium, in the block M65-M67 (Disorders of synovium and tendon).

Is M66.1 a billable code?

No. M66.1 is a header code with more specific child codes; report one of the billable codes listed above.

What category does M66.1 belong to?

It belongs to category M66 – Spontaneous rupture of synovium and tendon.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.