Hi I had knee replacement surgery on October 25th.  Since then off and on, I have had itchy skin primarily on the affected leg, but to some degree, on the other leg.  No real rash, but if I scratch it, it lumps up like hives.  This almost always happens at night.  In the daytime, I hardly ever itch, and there is no rash.
Hi, I think you might be suffering from dermatographism. Dermatographism could be due to a variety of causes which is a type of urticaria. You could take antihistamine empirically. But, I highly recommend you to consult your operating surgeon, and he may refer you to a dermatologist, if necessary. Hope I have answered your query. Let me know if I can assist you further.