It’s definitely the Paxlovid. I experienced the same thing. I have not been diagnosed with rheumatoid arthritis but do have arthritis in my hands, shoulders, and some moderate to severe stenosis in my neck and back which has caused leg weakness and drop foot in both feet. I have trouble with stairs and balance. I’m 64 years old. Since starting on Paxlovid I feel like I turned back the clock 10 years. No joint pain and walking normally without issue. Haven’t tried because of having COVID but feel like I could even run. Very frustrating as this tells me my condition could be treated. What is causing this premature aging I have been going through for two years now? Why doesn’t my back hurt anymore? Is is an anti inflammatory property in the Paxlovid? Need to figure this out because beside the cough from COVID I feel great.