Question: The patient came into the office with an initial encounter for a rupture of his right Achilles tendon. What ICD-10 code should I report for this diagnosis? Delaware Subscriber Answer: For a right Achilles tendon rupture, you should report S86.011A (Strain of right Achilles tendon, initial encounter). Achilles tendon rupture defined: The Achilles tendon, the largest tendon in the body, connects the calf muscles to the heel bone (calcaneous). Patients can rupture their Achilles tendon when they put too much strenuous force on it. Patients who have an Achilles tendon rupture will often feel instant pain in their foot or heel that may radiate along the back of their leg.