It is always my left knee, too, when it happens and what has helped me when upping the dose is slapping the detox footpads on at night whenever I experience this. The weird thing is what is coming out in the pads, now, very different from what was before supplementing with iodine. There will be these hard, white patches in the same place on the pads surrounded by a darker color (probably the kidney area of the foot, I should check this next time) and usually it lasts for a couple of nights then it is gone - the pads just resume a continuous darker color from the other toxins it yanks out. I think I get buildup in the kidneys every once in awhile and this sure helps to clear it out without having to take handfuls of supplements, which I hate.