I have had a lot of muscle and hamstring spasms, cramps and locked in flex in both the thighs and calves. I had both knees replaced at the same time. A great Physical Therapist that worked with me around the 4th and 5th days after surgery, helped me more than anyone else when he told me that I have to completely train all of my muscles at what to do to be able to function properly. This includes teaching them to relax, flex, extend, retract and anything else it takes to make them respond properly. As he spoke his explainations about particular muscles, he would message the area which helped me make the mental connection to that particular area. You must realize most of the proper healing accomplished is because your mind (the command center) needs to know what and where the problem is. I found that messaging an area that is problematic helps make perminant improvement. I still have problems with both knees functioning, flexing and feeling stable but it would all be much worse if I hadn't realized that the body has to heal itself, and I need to do everything I can, mentally, to help out.