Should Exercising Be Reduced Due To Knees Discomfort After A Replacement Surgery?

I have had partial kneereplacement in both knees on the 24 th July 2012 and I have discomfort in my boyhood knees .My whomI went to see recently said it could be soft tissue from doing too much excercise .I'm 81 years old ,and quite active ,and to slow down on excercise ,What do you advise,