Came across a neighbor at noon today, outside our back doors (he lives on the second floor of our condo; I live on the ground floor). He was slowly coming down his back stairs, lugging a wheeled device.
Then I saw that his left foot and ankle were in a big cast, and that the device was one of those crutch replacements that allows someone with a lower leg disability to get around by putting one knee on a platform and propelling themselves forward with the other foot.
I commiserated with Benj over his mishap (on the day after Christmas) and, linguist that I am, asked him what the (enormously useful) contraption was called.
A Roll-A-Bout, he said.
A photo of one model:
But that’s a trade name. Generically, these things are known as knee walkers, kneeling walkers, or knee scooters — three synthetic compounds in -er.
Of course there are names. If you need to use one of these things, you want a way to refer to it. The shorter walker and scooter are already taken for other useful devices, though they might be used, for short, in the right contexts, but the compounds and the trade name are entirely clear.