Kneel and stands are a great functional exercise that builds strength in the legs. Not only does it make the legs stronger, but it strengthens the ligaments and tendons in the knee.
I personally recommend doing 5 reps on one side and then switch to the other. Follow that for 3 sets. When that becomes way too easy, either increase sets or add a little weight by holding a light dumbbell in each hand.
If you are especially strong, try throwing a sand bag on your shoulder and do them that way. Switch shoulders as often as you switch sides.
How to do kneel and stands video: