What cardio exercises are the best for your butt/upper thighs?

Start doing squats, most cardio exercises will target the calves more than thighs and butt.

You cannot workout upper or lower thigh individually or more than the other their all one muscle.

Avoid incline treadmill this places more focus on the calves.

if you are doing squats appropriately it should not be tough at the knees. Make certain your knees keep covered up together with your feet and take a seat again. If your knees are going beyond your feet whilst you squat it is going to be more difficult in your knees and a much less strong determine.

You had best see your physician about that thighs