What Is The Cause Of Redness, Itching And Swelling In Ankles And Knees In A Diabetic And High Blood Pressure Patient?

My mother, who is 75 years old, a diabetic type 2, also with high blood pressure. She was admitted into the hospital approximately a month ago and broncitus and cardiomyopathy. The doctor changed her diabetic medication, she received some breathing treatments and was released. The new medication was making her very sick, and her regular doctor dropped her meds by half. She has been able to tolerate them better. But since her release from the hospital, her legs, from knee to ankles are swollen ,extremely hot, dark red, itching with severe muscle aches. She does not have a fever now nor did she have a fever when she was hospitalized). She is still week and since being released from the hospital a month ago. She went back to the hospital two days ago to have them look at her legs and they said it was cellulitus of the legs and put her back on antibiotics. She has been on 4 different kinds of antibotics since the beginning of October. I (her daughter) have looked this cellitus up on the computer and do not believe this is the problem. She has no open sores or cuts to allow an infection in under the skin. Any suggestions on how she might have gotten an infection in BOTH legs?