Why elliptical and bike are considered to be low impact compared to treadmill?

Question

I am wondering why elliptical and bike are considered to be low impact and better for people with bad knees. To me, these two seem to be using the knee joints more? Compared to walking or running on a treadmill

In: 7

Answer 1

To clarify a bit further —

Unlike a treadmill, on a bike or elliptical your foot never leaves “the ground” (the surface of the equipment), so there is no resulting impact as there is when you are walking or running on a treadmill. Walking/running on a treadmill requires you to lift your foot off the ground for each step. When your foot touches the ground again, there is an impact. Regardless of how minor it may seem.