Sorry but that sounds utterly bizarre. Do they not allow disabled people to work in their office then because they are “high risk” and not as quick moving as others in a fire drill?
If you need to work because of the money (don’t we all) then you have to just crack on with it unfortunately. I cannot see how a desk job is much different to sitting at home but maybe I’m being narrow minded. Assuming you are weight bearing, being a bit savvy about when you have lunch etc should help mitigate the busy periods where people are moving around much. I went through London, on the tubes on crutches non weight bearing and found everyone extremely helpful and considerate even at rush hour.
I’m sure if you were upfront with your work and said I need 15 mins mid morning and mid afternoon for physio and I need a desk near the kitchen or bathroom etc etc they would accommodate you.
I’m not suggesting you set back your recovery but I don’t think there’s much that you can’t do at work that you can do at home to aid it in your case.
Sorry to be blunt!