Be as close to the bar as you can to make sure your form of the squat is correct and your upper body can be in a good upright form during the squat. Put your weight through the bar with both hands to 'lighten' your body and unload the knee as much as needed. Push into the ball with your other leg as much as you can to increase the gluteal work. Move down into a one leg squat, aiming to let the knee travel forward normally. To return, 'push up' with your hands to assist the leg and keep the load off the knee as needed.