I Am Currently Being Treated For Spondyloarthrits. I Have Been

I am currently being treated for spondyloarthrits. I have been on plaquenil, sulfasalazine, and celebrex for a few years. Last July, Remicade was added every 6 weeks. I wonder if I am misdiagnosed. I still have chronic pain and inflammation in my feet and ankles and the muscles in my knees are quite wimpy. My muscles in general are weaker than ever before. Are there other diseases that have these symptoms?