Cat falling over, weak hind legs
My mom's cat Libby is a Russian Blue. She is about 6 years old. She probably is a bit mixed, since her grey hair is very long and her eyes are yellow. Anyway she is a sweet cat, barely makes a peep, and has always had robust health.
A couple months ago, she started to fall over and couldn't jump up onto the bed or couch. I googled her symptoms and found this thread. Frankly, reading other cat owner's plights with similar cat symptoms, was a very scary read.
We took her to the vet here in Pembroke Pines, FL and he quickly found a tenderspot on her spine. He took a couple of xrays and found some inflammation between two of her vertebrae. I don't remember which two, but it was where the nerves divert to the hind legs. He didn't know the cause or extent of damage to the disc, but suggested an injection of a strong anti-inflammatory into the disc. He advised that to go any further would require MRI's and that nobody spends less than $5k for that process.
He gave her the injection and it took about a day for it to take effect. Happy to report that she regained her full abilities and the problem was resolved.