I wear a small ... and I think we just went with the outline template on the package.
Though I did have the benefit to try them on in the store and compare to the other size.
That "small" sure boosted my ego as I don't think I have ever had small in anything before!
They are nice and stretchy, so while tight, they do not feel restrictive.
I think you may find them helpful for your arthritis.
I find them quite comfortable to wear, almost soothing and relaxing on my hands.
Definitely, you do not want them loose .... visions of quilting it into your work here!
Good Luck with your four day retreat ... how exciting!!