I've been experiencing a strange dull feeling just above my knees, as if they need to be popped. If I move my leg back and forth, the left one has a very quiet click until I feel 'better'; the right one is much quieter. There's no pain, and I've generally had this feeling in the left knee for as long as I can remember. I exercised yesterday. When I lift my leg (Angle 90 between the upper/lower leg) I feel a dull ache/soreness on the top of my knees. Is this something I should be concerned about?