Skin abrasion getting worse

have been treating with bacitracin, sulfur powder, but is not improving

Hello and thankyou for this excellent question.   A lot of wounds look like this, but the treatment is different depending on what's causing it.   For example, arthritis causes pain causes licking; the treatment in this case would be to treat the wound (I wouldn't have chosen those powders) but also an appropriate pain relief to stop the underlying cause.   Fleas cause pain cause licking; treatment for the wound, plus appropriate flea control.  Ligament or nerve damage causing plantigrade stance causing weight bearing in the wrong place causing skin damage; different approach again.   Allergy causing licking causing skin damage; still different.   Demodex causing hairless in that place; different again, often associated with underlying illness or stress.  Therefore my strong advice would be to show this to the vet.  They will start to rule out potential causes (if they suspect boney involvement eg arthritis they might propose radiographs to see if they're right) and find the correct treatment based on the most likely cause for your individual cat, rather than going through a number of 'wrong' treatments on the basis of guessing.

Because this area is centred over a joint, arthritis and urea-related concerns may be good things to rule out.   Your vet ought to triage the case to choose an appropriate appointment time for you.