You could leave them in place and work around them. The leaves and compost will only add a temporary increase in height to the soil level. Once they decompose, they will shrink significantly in volume and you won't even notice any increase in height.

Alternately, if it's just a few plants involved, you can lift them out temporarily while you prepare the beds and then replant. It's really your choice :-)

I can sympathize with you re: the arthritis. I also have arthritic knees and it does complicate gardening somewhat. If I kneel, they seize up and lock and I can't get back up easily so I do all my gardening bending over. And that's not helping my aging back much, either :-) Ahhhh, the many joys of getting older!!

As always, gardengal48, has a complete & correct answer.
I was wondering(mainly because I will need this someday) if flagstone or pavers between the beds make it easy to use a low seat to work in the beds.

Thanks for the great answer! I think I will leave the plants since monarda and sedum seem to be stunted when I transplant them. Last year I bought a "grasshopper" roling seat from Target and I could sit on that for the edges. I also have a kneeling bench but I can't kneel anymore. My beds weren't very full so I rolled into them to plant, weed etc. I know this will compact soil so I don't want to do that this year. Pavers are a good idea and could be placed inside the bed here and there to stand on. My new husband has just figured out that I am going to do it anyway so stop protesting and HELP ME! Thanks ladies.