M66.18 Rupture of synovium, other site

Billable ICD-10-CM code, FY2026.

Applies from 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

Applies from M66.1 Rupture of synovium

Applicable to

• Rupture of synovial cyst

Excludes2 (not included here)

• rupture of popliteal cyst (M66.0)

MS-DRG index

Defines the logic of DRG(s) 557-558 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 727.59 Other rupture of synovium (approximate)

Code annotations containing back-references to M66.18

Back-references to M66.1

• Type 1 Excludes: M71.3 Other bursal cyst ("synovial cyst with rupture (M66.1-)")

Back-references to M66

• Type 2 Excludes: M62.1 Other rupture of muscle (nontraumatic) ("rupture of tendon (M66.-)")

Diagnosis Index entries for M66.18

• Rupture, ruptured › synovium (cyst) › specified site NEC

Nearby codes

• M66.175 Rupture of synovium, left foot
• M66.176 Rupture of synovium, unspecified foot
• M66.177 Rupture of synovium, right toe(s)
• M66.178 Rupture of synovium, left toe(s)
• M66.179 Rupture of synovium, unspecified toe(s)
• M66.18 Rupture of synovium, other site (this code)
• M66.2 Spontaneous rupture of extensor tendons
• M66.20 Spontaneous rupture of extensor tendons, unspecified site
• M66.21 Spontaneous rupture of extensor tendons, shoulder
• M66.211 Spontaneous rupture of extensor tendons, right shoulder
• M66.212 Spontaneous rupture of extensor tendons, left shoulder