I had asked for some additional information and have not heard back.
The most common type of arthritis is osteoarthritis, or degenerative arthritis, which is due to wear and tear within the musculoskeletal system. Not only can it affect the foot, it can also affect the neck and lower spine, as well as most joints in the body. It is not surprising that blood work is negative, because blood work is usually negative in people with osteoarthritis. Blood work is better at detecting certain types of arthritis that have a greater inflammatory component, such as rheumatoid arthritis.
However, it is actually more complex than simply whether osteoarthritis is present everywhere that you have pain. There are different manifestations that can occur in different locations, and the primary concern in someone with back pain is whether the degenerative changes is also affecting the discs in the spine, and particularly whether the discs may be pressing on the nerves as they exit the spine. Advanced imaging studies, such as an MRI, would be the usual method for identifying the extent of any disc involvement
In addition, it is also possible that fibromyalgia could be present. Fobromyalgia can occur as a complication of any condition that causes chronic musculoskeletal pain. It would be the findings on exam that would raise concern that fibromyalgia could also be present.
So, with negative blood work, it is unlikely that rheumatoid arthritis is present. The most likely type of arthritis is osteoarthritis, although the exact manifestations could be better defined by advanced imaging. It is also possible that fibromyalgia could be present, although it would be the findings on exam that would support whether that diagnosis is also present.
If I can provide any further information, please let me know.