what causes popping in knee?
<answer> Chondromalacia, a condition where the cartilage under your kneecap is starting to degenerate. <context> Most common reasons your knees pop or snap: 1  Chondromalacia – Is a condition where the cartilage under your kneecap is starting to degenerate. 2  As the cartilage degenerates the surface can become rough. 3  That rough surface will rub against the femur and cause snapping, clicking or popping.