Do your knees click, pop, or crunch when you squat? out. That sound is called Crepitus, and it might mean your "internal Teflon" is wearing Here is a 3D breakdown of Osteoarthritis (Bone on Bone). When the smooth cartilage wears away, your raw bones grind together like sandpaper. In this video: What causes knee clicking (Crepitus) How cartilage protects your bones The "Sandpaper" effect of arthritis #shorts #kneepain #anatomy