Now that you mention knees, it's time to bring you up to date on a situation with my own, that being my left replacement knee. I got up to get something out of the kitchen about 10 days ago, and I damned near didn't make it. My left knee felt like it was going to go through an explosive disassembly on me. I grabbed my cane, made it back to my chair, and sat down, but the pain didn't subside - it got worse, climbing up to a 9.5 on the 0-to-10 scale. It made me sick to my stomach and drew tears.
I managed to get an appointment with the knee surgeon's office two days later. They didn't see any structural problems on the X-ray, but they were able to tell that the joint was loose when they gave it the side-to-side shake test. They suggested doing surgery to put in shims to tighten up the mechanical joint, to which I agreed. They've already called to schedule. I've got a cruise-convention that I can't miss at the end of March, so the surgery won't take place until April 2nd. Until then, I'm using the cane 100% of the time, as opposed to just outside of the house before the incident occured.