You will need an assistant for this exercise.
Lie on your back with a buoyancy collar around your neck and a noodle under your hips.
Place an inflatable ring under your unaffected leg.
Ask your assistant to stand at your feet facing towards you.
Bend your affected knee and ask your assistant to clamp your ankle between their knees.
Ask your assistant to place the heels of their hands around your lower leg behind your knee.
Your assistant shall then gently pull towards them before pushing away at the top of your shin in a small movement.
Continue to repeat this movement.