M66.171 Rupture of synovium, right ankle

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 M66.171

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.-)")

Nearby codes

• M66.15 Rupture of synovium, hip
• M66.151 Rupture of synovium, right hip
• M66.152 Rupture of synovium, left hip
• M66.159 Rupture of synovium, unspecified hip
• M66.17 Rupture of synovium, ankle, foot and toes
• M66.171 Rupture of synovium, right ankle (this code)
• M66.172 Rupture of synovium, left ankle
• M66.173 Rupture of synovium, unspecified ankle
• M66.174 Rupture of synovium, right foot
• M66.175 Rupture of synovium, left foot
• M66.176 Rupture of synovium, unspecified foot