I'm not sure it would work with a knee surgery but these were around last year and I found didn't disrupt the flow too badly.

https://www.amazon.com/KneeRover-Steerable-Scooter-Crutches-Alternative/dp/B006G0M77C?keywords=knee+scooter&qid=1533883509&sr=8-1-spons&ref=mp_s_a_1_1_sspa&psc=1