I'm not sure if this would count as jumping, but you might want to try it.
1) Squat down in a wide stance (feet shoulder width and a half or wider) with toes pointing forward.
2) Straighten right leg to stand up, whilst bringing left leg up to perform a "front kick". For a front kick, bend knee first, then extend leg with a flexed foot to kick with the heel.
3) Bend left leg at knee, before replacing on floor in wide stance and squat down again.
4) Repeat front kick with right leg, repeat with left ad infinitum 'till you fall on the floor!
We usually do this with our hands protecting our head, so you should be able to do this with your arm in a sling. Hope the instructions are clear.
Step-overs on aerobic step(keep adding rings as you get stronger); one legged step-ups without putting weight on the "off" foot (turns into a one legged squat); endless lunge variations with pulses, side lunges, lunge twist, etc.
Hmmm...if you can get someone else to help you, Robert's idea could be modified to squat nice and deep with weight. Put 2 flat benches about 2 feet apart, get someone else to attach a plate onto a belt for you, and stand with one foot on each bench and do squats. You'll be able to let the plate dangle between the benches so you can squat low enough, but you are going to need help.
Can you get up and down off the floor? I attached cables to ankle cuffs for a client who had a sprained ankle and had her lie down and pull her knees up one at a time- kind of a reverse squat.
Step Ups, Butt Blaster, Lunges, Squats, Plies, Leg Extensions, Lying Leg Curls, Seated Leg Curls, Standing Leg Curls, Hip Abduction, Hip Addcution, High Incline/Low Speed on Treadmill, Squat with Abduction (lift one leg out to side when you stand up), Lying Leg Raises (Inner and Outer, can lay weight on leg for added resistance), Cable Leg Raises (Inner, Outer, and Backward), Leg Press (Unilateral and bilateral), Calf Press (Unilateral and Bilateral).
Put 2 flat benches about 2 feet apart, get someone else to attach a plate onto a belt for you, and stand with one foot on each bench and do squats. You'll be able to let the plate dangle between the benches so you can squat low enough, but you are going to need help.
There are a bunch of leg exercises you can do with one of those cable gymnasium-contraptions, too. Attach an ankle-cuff to your leg and a cable (lowered to the floor) and you can do abductions, adductions, forward kicks, donkey-kicks... and all you have to do for weights is change the pin.