I know this is an old thread, but I just came across it and it's both encouraging and scary.
Encouraging because I thought I was the only one whose condition suddenly took a dive, after being relatively minor (albeit undiagnosed) for years. Scary because I've realised how bad it can get.
I can date my slide pretty precisely, since it was when I partially ruptured the first of both Achilles tendons. Then followed 18 months of inappropriate treatment for imagined inflammatory arthritis (including mega doses of steroids), the diagnosis mill, culminating in my GP telling me I needed to pull myself together, because my obsession about getting a diagnosis. At that point, the NHS having given up on me, and assuming I was just making a big deal about nothing, I went private.
I remember thinking, when I was diagnosed, that at least I didn't have problems with subluxations, and at least my upper body was fine. Well, since then, I've had problems with my shoulders, elbows, various joints "popping out" (albeit not full dislocations), spasms in my hands, various bits of my body going numb in the night, and then last week, my knee gave out on me as I was going downstairs, and I fell. I wasn't badly hurt, but since then I've had problems with my knee "going", and just collapsing when I put weight on it bent.
So I suspect I am deteriorating and its scary. As well as painful and I so wish I had a GP who really understood HMS, instead of constantly going on about fibromyalgia, which I now have as a secondary condition.