I'm 28 years old, currently very active at the gym (kickboxing) and watching my diet. I've been having constant muscle twitching under my left knee towards my shin for about two weeks now. It's a sharp twitch, but with no pain. I can feel the twitch, but you can't see it. It happens when I walk, put force on my left leg or move it a certain way. There is no tingling or numbing, just the constant snapping twitch when active. Just today I noticed some discoloration of the skin around where the twitch is located. It's a slight green, like bruising, but it doesn't hurt to the touch. What could be causing the annoying twitching? Is it something I should be worried about? I thought perhaps I might have irritated a nerve when kicking the bag at the gym. Or it might be related to my thoracic back pain?