The retrocalcaneal bursa is located between the Achilles tendon and the heel bone. The bursa is like a water balloon that lubricates between the tendon and the bone to reduce friction.
Injury occurs when the bursa is excessively irritated which may be due to tight shoes or tight calf and Achilles or alternatively poor biomechanics.This occurs, when the bursa, located between the calcaneus and the achilles tendon gets impinged repeatedly (van Sterkenburg et al., 2010) and causes an inflammation.
Management should include the PRICE regime, altering biomechanics / shoes and training protocols and improving flexibility of the calf and Achilles.
Van Sterkenburg M.N. et al., 2010, Appearance of weight-bearing lateral radiograph in retrocalcaneal bursitis, Acta Orthopaedica, 81(3), pp: 387-390