I would recommend a two-shouldered carrier of some kind that spreads evenly over both shoulders like a wrap carrier. I have an Ellaroo which is a non-stretchy woven wrap. I believe the Moby is a stretchy wrap.
And I totally had tendinits when my DD was between 6-12 months!! I had it in my wrist from holding her down to change her friggin' diaper! :LOL And she used to arch her back and twist around all the time to get down from my hip (like at the store) and I'd hold her in my 'death grip' to keep her safe and it had a very bad affect on my hand. I had a few osteopathic manipulations that really did no good. The best thing for me was ibuprofen at regular intervals (and trust me, I NEVER recommend drugs of any kind for anything), and as time went by and I carried her less, it faded away. She was also a HUGE child and I had a Maya Wrap that I used constantly because I didn't know there was anything else out there at the time. It killed me and the rings slipped constantly. A lot of that was her weight being incompatible with her age and she seemed even heavier. And she slouched back all the time causing me to have to stand crooked. If this baby comes out as huge as DD was, I plan to get him in a two-shouldered carrier he cannot escape from (Kozy, Ellaroo) and I think it will make things much better - at least on my hand! :LOL