Single Leg Squats

Generally speaking, Yes, this is a very good exercise for jumpers knee.

If you have not done so already, I would first make sure to get diagnosed by a Doctor to make sure it is jumpers knee.

Mike Reid

I would have to agree with you that I do give a bit of push with my "non working" leg when using the higher bench but the involvement is reduced by keeping my toes up.

It is neither good/bad; but the important thing is that it is the same on both sides.

One of the benefits of single leg exercises is to work on left/right strength imbalances. If you are only assisting with the non working leg on one side then this will certainly skew your perception of an imbalance.

Mike Reid