See the above post which includes information about tendonectomies - they render the cat unable to use the front part of their paws, which then atrophy, and flop, causing the animal to walk unaturally on the hind part of its paws.
This can then cause a host of other problems, as limping always does.
I prefer the word amputation to declawing, as declawing sounds so benign, and I think people should always be aware of what it is they do - sugar coating the words doesn't help.