My Knee Aches, And After Sleeping Or Sitting Very Long

My knee aches, and after sleeping or sitting very long , like over 30 minutes , if i stand I must stand still a few moments before i can trust stepping on it, but it with a deed limp that will disappear after walking a bit, some pain, and the only swelling is above the knee, in upper right side [right leg] the amount of swelling is apparent if your looking for it, it's pear shape. I can stand, evenly distributing my weight with no pain. However If I try walking the pain will reappear causing a deep "limp" for me and my hip to ache as I try to compensate. I cannot recall any injury, but I suspect I might have hyper extended the knee, while at work or yoga.