Split Lunge
Get those legs wide as if you are doing a lunge. Keep feet fixed. Lower yourself until your knee touches the ground and then come back up. Keep your back straight and make sure you push backwards as you come up to avoid excess pressure on your knees.
Split Squat
From a standing position. Go to kneeling with the aim of getting your knee in line with your ankle. When pushing up remember to keep your back as straight as possible, and push back either through the toes (exercise quads) or the heel (exercise hamstrings and glutes).
Squat Jump Forwards and Backwards
Simple squat jumps forwards and backwards. Keeps those toes pointing forwards and ensure a soft impact for those knees.
Sumo Squat Pulse
Legs wide, and toes pointing out at 45 degrees. Do a small small squat with a pulse at the end and attempt to get the whole of your feet off the ground. come back down on your toes and go down to a low squat position.