I have knee probs to and have never had any probs with tenders, but i am going on this ship on 30th Oct,to Caribbean, and have done all these islands twice before on other ships and they have never had to use a tende.
There are well trained crew that will help you get on the tenders. if you can stand up.the seas are not to ruff most of the time .hope this helps you.
No there should be no problem at all, they are quite easy to board so i think you'll be ok and there are people there when you board the tender who help you on and off the boa.
I have just returned from the OV2 Villas and Vineyards cruise. The criteria for going on the tenders was that people should be able to walk with assistance. Hopefully you'll be OK.
We have just come off the OV2 they were always really helpful staff with many of the people with wheel chairs and disabilities.
I am scared going into the smaller boats - but i was fine.
We called at St. Raphael. We got on the larger blue boat to go ashore, but to come back had the OV2 own. Both were fine.
I am sure you will enjoy it - it was lovely.