When Im being active or on slippery paths one of my knees decide to pop, move out of place, and then come back to normal after this i feel pain for at least 3 mins depends on how hard it popped. When I bend my knees I can hear crunchy noises and I rarely find it quite painful to walk or go upstairs. I onced popped my knee so hard I couldnt walk but my knee always come back in place.