Rheumatoid Arthritis Support Group
Rheumatoid arthritis is a chronic, inflammatory, multisystem, autoimmune disorder. It is a disabling and painful condition which can lead to substantial loss of mobility due to pain and joint destruction. The disease is also systemic in that it often also affects many extra-articular tissues throughout the body including the skin, blood vessels, heart, lungs, and...

I sounds like people with RA and other inflammatory diseases can get flareups like this with much less overuse, so it may be possible it was pushing the shopping cart was the trigger. Who knows?
I'm sorry you're suffering so badly and I hope PM can help you quickly.
I finally had surgery and the relief was wonderful. I've heard that some people get it back even after the surgery but I never did. I was told it was an overuse injury that built up over the years. Now I wonder if it was the first sign of RA. That's also about the time I started getting bursitis. I'm sorry about your pain. I know how bad that can be.
LionPrincess, tendonitis is inflammation of a tendon. Bursitis is when the bursa (sac of water between joints) leaks and you get bone-on-bone pain. - very painful.