What Causes Blisters And Swelling On The Knee Replaced Leg?

Hi my mother in law is 78 years old and was in relatively good health. She had a knee replacement done in the middle of April, all seemed to be going well with the exception of very large blisters on her feet and swelling of her operated leg when she left the hospital. Her home nurse told her one of the blisters was definitely infected. Since then she has had several trips to the hospital complaining of extreme pain in the groin and leg, the same side as the blister. She is now back in the hospital in poor condition, they have diagnosed MRSA but we are not getting answers and she is declining since being there on Friday. Question is should I be bringing up the Pyomyositis or the possibility that this has spread to perahaps even the bone or bloodstream. She is very disoriented cannot sleep or get comfortable because of the pain...and seems very incoherent at times. The rest of the family puts this down to being on pain killers or depression...please help because I really feel my mother in law is in danger and they are not acting quick enough. Thank you. Sue