Heel Pain with swelling. -possibly?

My father is suffering from heel pain (left ankle) with swelling for 1.5 years.He has consulted various orthopedic doctors. First doctor asked him to follow physiotherapy procedures along with pain killers. With no relief we consulted another doctor. He prescribed steroid injection. Initially his pain subsided for 2 months but became very acute post that. We consulted third doctor and he asked us to do Ultra sound.This test suggested MRI to rule out marrow oedema.MRI Impression is "Diffuse marrow signal alterations in the calcaneum bone with ill-defined areas of bony erosions &marrow oedema -possibly ? Infective etiology(Tuberculosis to be ruled out). Small Osteochondral erosion in the medica aspect of talar dome."So, doctor suspected that he has Calcaneal TB and asked him to undergo biopsy.The doctor took 2 samples; from synovial tissue and left calcaneum bone.The AFB stain reports were negative for both samples.Fungal culture was also negative for Mycobacterium sps.Please advice