I took a slight pain in my knee the other day, not too bothersome but since went behind my knee, a sharpe pain, then naggy one and is now in the calf of my leg , doesn t bother when when I m sitting but oh when I get up its hard to put my weight on it, then as I walk it eases until I walk to long, then it gets bad.Also their seems to be a spot on the inside of my knee, that when I put my legs together when sleeping it really hurts...What could be causing all of this, I didn t trip, fall or twist the leg, was just walking normally