Inflammation from the bursa at the rear of the heel is termed Retrocalcaneal Bursitis. Repetitive stress or friction about the back with the heel results in the bursa to swell causing heel pain and tenderness, swelling and ankle stiffness. Normally related to Achilles Tendonitis and Haglunds Deformity.   Well being's written https://www.theorthopaedicandpainpractice.com/the-definitive-guide-to-diagnosing-and-treating-ankle-pain-in-singapore/