Spontaneous rupture of extensor tendons, unsp lower leg

This code signifies a non-traumatic tear of the extensor tendons in an unspecified lower leg. This typically occurs due to degenerative changes within the tendon, rather than an acute injury or external force. The rupture leads to impaired extension function of the foot or toes.

Apply this code when documentation clearly indicates a spontaneous (non-traumatic) rupture of an extensor tendon in the lower leg, and the specific leg (right or left) is not specified. This diagnosis is supported by findings such as sudden onset of pain, inability to extend the foot or toes, and imaging (e.g., ultrasound, MRI) confirming tendon discontinuity without evidence of external trauma.

• Ensure documentation explicitly states "spontaneous" or "non-traumatic" to differentiate from traumatic ruptures.
• Avoid using this code if the specific lower leg (right or left) is identified; instead, use the more specific codes M66.261 or M66.262.
• Do not confuse with M66.3- (spontaneous rupture of flexor tendons) or M66.8- (other spontaneous ruptures of tendons).