What Causes Bursitis And Adjacent Reactive Marrow Edema?

I recently had calcaneal spur and hoaglands deformity surgery. In recent MRI there states several issues, one of which is bursitis with adjacent reactive marrow edema at the posterior superior portion of the calcaneus . Also, a dorsal enthesophyte of the calcanueus with nodular ossification in the distal Achilles. As I stated there were a few other items mentioned, but if someone could explain these too me that would be wonderful.