Spontaneous rupture of flexor tendons, unspecified lower leg

This code signifies a non-traumatic tear of the flexor tendons located in an unspecified part of the lower leg. This condition typically results from degenerative changes within the tendon structure rather than an acute external injury. It leads to impaired function and pain in the affected lower leg.

Apply this code when documentation clearly states a spontaneous (non-traumatic) rupture of a flexor tendon in the lower leg, without specifying laterality or a more precise anatomical location. This code is appropriate when the physician's notes indicate a degenerative etiology for the tendon tear.

• Ensure documentation explicitly states "spontaneous" or "non-traumatic" to differentiate from traumatic ruptures.
• Avoid this code if laterality (right or left) or a more specific anatomical site (e.g., posterior tibial tendon) is documented; use a more specific code from the M66.3- subcategory.
• Do not use for ruptures due to overuse or repetitive strain, as these may fall under different code categories.