My husband is on Amoxicillan 500mg. for infection on right knee, due to a knee replacement.  He took the antibiatic a week and a 1/2 ago for 4 days and it didnt do the job.  So the Dr. put hin on it for 10 days, although he has been on it only 6 and now has a rash and itch and a little swelling.  We have put Benedryl and ice on the area.  And nothing seems to work.
Hi rash itching and swelling can be due to graft versus host reaction.it is due to your knee replacement .it can be cured by a broad spectrum antibiotic.anti-inflammatory agent and steroid like cyclone 30 mg daily tapered to 10 mg daily within 3 weeks. If not cured use immunomodulatory agents .like camisole vitamin C and plain zinc can help