When the gluteal muscles are weak, you will notice increased movement of the trunk toward the side of weakness, and the knee will cave in toward the midline. Are your glutes weak or strong?
Start to observe what you do when you go up/down stairs: do you turn your foot out to give yourself more support, does your knee drift to the midline, do you shift your torso over to the planted leg to make it easier to step up? If yes, then your glutes are weak
What happens when you bend down to pick something off of the floor or transition to get in and out of a chair: do your knees come together? If yes, then your glutes are weak.