I am 56 years old and other than running while in the army, was never a sports or gym person, so little abuse to my frame. My right knee usually works fine, with occasional 'slippping loose' when standing or walking, and it pops at times, but no pain or problem walking lond distance or carrying a load.

This last year, at first while sleeping, but now multiple times during the day, when I leave my leg bent while sleeping or working, eventually it becomes uncomfortable or in slight pain. When I stretch out the leg to releive it, I get extreem pain, right in the knee. The further I stretch it, the more pain. The pain feels like a cramp would, but does not extend beyond the immediate area of the knee. The longer I keep it bent and inactive, the worse the pain of trying to straighten it out. So far, I have been able to strighten it after some painful effort.
Nothing I've read seems to address this type problem. Any suggestions what I might read about that is targeted to this type knee problem?
Charles