Swelling of knee with pain (no injury)

Hello to Everyone! I am a contributor to this group concerning TKR. I had TKR for my right knee two years ago, and it is now doing okay. My left knee has severe osteoarthritis and I get a cortisone shot every 3-4 months for it. Right now, I am on vacation in FL for two weeks. I was walking off the beach this morning and all of a sudden, my left knee started to hurt and swelled quite a bit! I didn’t injure it…….just happened on its own! Something similar happened to me with this same knee over a year ago, and they told me that it was a Baker’s Cyst and all that I could do for it was ice it, elevate it and rest it. I am wondering if this is happening to me a second time now. It is very swollen all around the kneecap and it really hurts to put weight on it. I started icing it and elevating it about two hours ago, and took Advil and Tylenol. My husband went to the store and bought me a knee brace. Has anyone else had this happen? If so, any additional tips that you could be would be so appreciated! Hard to be on vacation and have this happen out of the blue! Thanks in advance for any suggestions or input! MaryAnn from Boston (Mabfp3)