Feel pleasure in my leg from injury?

So, this is getting to me. I have had a knee injury for a long time and im waiting for surgery where i "have" to keep it straight but i bend it. Its as if theres fluid, weakness amd pain. But when i bend it at an obtuse angle (for those who dont know, larger than 90 degrees) i feel like pleasure. Now, i dont always bend it. I bend it about 3 times a day or so. Not the kind og pleasure in a vagina or penis but, almost as if something is rushing through my leg making it almlst shake and i sometimes moan. Almost like how some people with certain types of blood loss cases feel pleausre. So is it normall to feel pleasure when you bend your knee ocasionalky after a injury?