M66.261 Spontaneous rupture of extensor tendons, right lower leg

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

MS-DRG index

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

Approximate ICD-9-CM (GEMs)

• 727.66 Nontraumatic rupture of patellar tendon (approximate)

Code annotations containing back-references to M66.261

Back-references to M66

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

Nearby codes

• M66.25 Spontaneous rupture of extensor tendons, thigh
• M66.251 Spontaneous rupture of extensor tendons, right thigh
• M66.252 Spontaneous rupture of extensor tendons, left thigh
• M66.259 Spontaneous rupture of extensor tendons, unspecified thigh
• M66.26 Spontaneous rupture of extensor tendons, lower leg
• M66.261 Spontaneous rupture of extensor tendons, right lower leg (this code)
• M66.262 Spontaneous rupture of extensor tendons, left lower leg
• M66.269 Spontaneous rupture of extensor tendons, unspecified lower leg
• M66.27 Spontaneous rupture of extensor tendons, ankle and foot
• M66.271 Spontaneous rupture of extensor tendons, right ankle and foot
• M66.272 Spontaneous rupture of extensor tendons, left ankle and foot