I think getting old may have something to do with it (speaking as an ophthalmologist). I've noted the almost daily addition of a new creak, pop, or pain. I do agree that you should have it checked early on to make sure there isn't something more serious occurring. Dirty Dog is correct. The synovial fluid is the natural lubricant of joints and you want that in there. When joints move in certain ways it can create negative pressure across the joint space and you get a brief vacuum bubble that can pop as the joint returns to natural alignment. If the knees check out as stable and you have no pain you're probably good to go. If you continue to practice MA you can expect some degree of arthritis in joints that get overstressed and then you will hurt. You will. You will. But where would the fun in life be if we gave up every wonderful thing just because it might not be perfectly benign. As an aside, some recommend choindroitin sulfate supplements. I take them and I have no idea if they are helping.
