Hi L5S1_ArthritisQueen,
Welcome to our Mattress Forum! 
I am sorry to hear about your discomfort upon waking up in the morning due to the post-surgery “arthritic back” . As you do have some very specific health considerations, nothing can replace your own personal testing. You’d obviously want to consider something that allows for enough surface comfort, and also assists with pressure point relief, while still overall being resilient enough and provide enough support while sleeping. Overall, the two basic functions of a mattress are to support and to provide comfort (you can read more about the basic functions of a mattress here ), with posture and alignment being the first priority and then comfort/ pressure relief “plushness” coming second. I’d also suggest that you consider the adjustable bed after you found the best suitable mattress for you.
When considering any mattress, please be wary of any claims of health benefits, including the relief of back pain. While certain people may respond better or worse to different products, there is no mattress that can make sure a claim with any degree of reproducible certainty. I just wanted to mention that as a cautionary statement as many people tend to get hypnotized by marketing stories. Also, the ~$&K price tag or manufacturer name is not an indicator of quality and suitability, so I’d do a hard reset and start with the first step to find your best match.
The first place to start your research is the mattress shopping tutorial here (there is a condensed version of it at the end of that post) which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps, more importantly, know how and why to avoid the worst ones. Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well he will sleep), durability (how long he will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
When assessing any product, also be sure that you find out information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
While we can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see post #2 here ).
Hopefully, the information in this reply will give you a good start but if you are stuck with any of the steps in the tutorial or have any other questions we can help with then you are certainly welcome to post them on the forum.
Phoenix