Separation of muscle (nontraumatic), left lower leg

This code signifies a spontaneous or atraumatic separation of muscle fibers in the left lower leg. This condition is characterized by a tear or rupture of muscle tissue that is not caused by an external injury or trauma. It often presents with sudden pain, swelling, and impaired function of the affected muscle.

Apply this code when documentation clearly indicates a non-traumatic muscle separation in the left lower leg, such as a spontaneous rupture of the gastrocnemius or soleus muscle. Supporting documentation should specify the absence of an acute external force or injury as the cause. This code is appropriate for conditions like a "tennis leg" when it occurs without a direct impact or fall.

• Ensure documentation explicitly states "nontraumatic" or describes a spontaneous onset without external injury.
• Differentiate from traumatic muscle strains or tears (S86.x codes), which involve an external force.
• Specify laterality (left lower leg) as this code is highly specific.