Is It Normal To Have Incision And Sensitivity On Skin At The Surgical Site?

I am a 46 yr. old female. I am 5 ft 3 inches & weigh 170 lbs. I am allergic to penicillin & sulfa. I recently had arthroscopic knee surgery on my right knee. When I removed the bandage, there was a big red spot in between the incisions on my knee. The skin was very sensitive to touch. Very much like a burn. Is this normal? The spot was slowly growing larger until I went back to the Dr.s and he put me on an atibiotic. My physical therapist is concerned. Is this normal after surgery? The antibiotic has seemed to help some but the spot is still there & almost as big as it was. I also had a cortisone injection on the lower inside left side of my knee due to bursitis. This was administered during surgery.