Be aware that treadmill running is quite different from a physiological perspective as well. In layman’s terms, as the belt moves below you, your running style becomes more one of just falling forward to stay ahead of the belt, and you use considerably less drive from the hips and thighs...
You really need to be paying decent money. The cheaper they are, the shorter and narrower the running surface, to the point where the really cheap ones (less than £400) are so short and narrow that you have to completely change your running gait, making it counter productive, and a clothes horse...