I picked up a raw stainless steel Phicen skeleton (armature in the world of stop motion animation) on eBay to do some testing with. It's a pretty remarkable piece of craftsmanship. Construction uses a pair of front/back stamped and shaped stainless plates that are riveted together; the knees and arms are fitted with crimped bands to provide clamping pressure on the ball/socket joint. The sockets are scalloped in places, presumably to act as detents and help lock in a pose. It also appears that the length of the legs and arms is adjustable at the time of crimping their bands. Looks like with that design feature they could adapt the same skeleton and components to taller figures. On the shins there is a slight back curve to emulate the actual bone structure.
Color me impressed.