M66.861 Spontaneous rupture of other 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)

• 727.67 Nontraumatic rupture of achilles tendon (approximate)

Code annotations containing back-references to M66.861

Back-references to M66

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

Nearby codes

• M66.85 Spontaneous rupture of other tendons, thigh
• M66.851 Spontaneous rupture of other tendons, right thigh
• M66.852 Spontaneous rupture of other tendons, left thigh
• M66.859 Spontaneous rupture of other tendons, unspecified thigh
• M66.86 Spontaneous rupture of other tendons, lower leg
• M66.861 Spontaneous rupture of other tendons, right lower leg (this code)
• M66.862 Spontaneous rupture of other tendons, left lower leg
• M66.869 Spontaneous rupture of other tendons, unspecified lower leg
• M66.87 Spontaneous rupture of other tendons, ankle and foot
• M66.871 Spontaneous rupture of other tendons, right ankle and foot
• M66.872 Spontaneous rupture of other tendons, left ankle and foot