Well, I wasn't going to drag this thread up to the top again, but I decided that in my cloud of misery, there is the silver lining of a bit of learning.
My leg, if anything, has been feeling worse. It is still very swollen, turning yellow/black/blue (right down to the ankle), extremely painful and tingling. I ran out of good pain drugs over the weekend, and in desperation I went back to the emergency ward yesterday. Fourth visit in five days.
It's a small town, and we all know the best docs, and I was lucky to see the very best and nicest. He reassured me that the pain, swelling and discolouration was just (!) the Baker's Cyst. Oh, and he referred to it as "the biggest Baker's Cyst known to man". I didn't know whether to laugh or cry. Actually, I did both.
So here is the part that helped me understand what was happening:
Even though I have a titanium knee, the joint tissues are still producing synovial fluid. The psoriatic arthritis is inflaming those tissues and they are overproducing fluid. The pressure builds, and the fluid overflows into the space behind the knee. In my case, this fluid-filled sac grew and grew as it filled with the overproduction of synovial fluid. Then, at 8 cm, it ruptured and the (inflamed) joint fluid (probably mixed with some blood) is now seeping down through my muscles and other tissues in the leg. Hence the swelling, inflammation and discolouration. And the pain, of course.
What did they do? Well, they aspirated my knee and sent the goo (it was thick and yellow, like mucilage!) to the lab. Then they gave me a shot of cortisone in the joint space, in the hopes of quelling the inflammation a bit. They hope that the cortisone will filter down into the leg to calm things down a bit. If I'm still in bad shape by the end of the week, they said they could aspirate the cyst itself and inject it with more cortisone. Oh, and they gave me a tramadol/acetaminophen painkiller, which dials the pain down from "excruciating" to just "bad".
For now, my knee feels a bit looser than before, but the leg is still painfully swollen. Every step I take makes me wince. I will take the offer of cyst drainage and infusion at the end of the week if I need it. Meanwhile, I'm lying here with my leg up, being thankful for small mercies, I have a nice, light little laptop, and fingers that can still type. And thank goodness I just happen to have a rheumy appointment next Tuesday.
I've decided that PsA is a thief and a vandal: it is wrecking my body and stealing my life.