Hi! I joined an excersizing group last December, and we did alot of work running up and down stairs. My knee began to hurt, pop a lot, and become weak. I tried to ignore it but every time i excersize, it comes back. There was a time shortly after the surgery where i was under a heating blanket and it burned the skin of my knee on a certain spot. (not sure if relevant?) i try to kayak in my swimming class, but the certain way you have to bend the knee causes it to go completely numb from my thigh down to my toes in a matter of ten minutes. do you have any idea what is wrong?