Starting position Using an exercise ball stand, with your back to the wall, holding the ball against the wall in the middle of your back.  This will help to keep your back straight and focus the work in and around your knee joint.
	Double Knee Bend This exercise can be quite strong especially if your knees are weak so start with bending both legs together, this is both a warm up and a strengthening exercise.  Only bend your knees to a comfortably uncomfortable angle.  If your knees are damaged or swollen then just do this exercise 10 times every day until you can feel your knee strength returning. As you bend exhale and contract your pelvis floor muscles and as your straighten your legs exhale and maintain the pelvic floor contraction as much as you can.
	Single Knee Bend starting position Stand tall and lift one foot off the floor. Bend the standing leg carefully.  This is much stronger than the previous exercise so take care not to bend too far.  If the exercise is still too strong then return to the first exercise, The Double Knee Bend, or do this exercise with your toe tips of the non weight bearing leg on the floor.  Repeat 10 times.
	Single Knee Bend As you bend the weight bearing leg exhale and contract your pelvic floor muscles, maintain your grip while straightening your leg and exhaling.Go slow.
	Repeat on the second side. Repeat as before on the second leg being aware of differences in knee strength.  You will notice a significant improvement within a week.  Continue until the exercise becomes relatively comfortable.

Additional Notes:
Keep the back of your neck long and your shoulders relaxed.
If the balance is difficult when doing the single leg bend, due to weakness,  then you can do the exercise in a narrow hall way with your fingertips on the wall at chest height to help with balance initially.