Prostheses in the Late Middle Ages and in the Renaissance and in Modern Times were divided into" work "and" cosmetic ". So, "working" prostheses were instruments attached to the stump. There were also "cosmetic" dentures, luxury items available only to the wealthy. They had different functionality, mostly they only performed cosmetic prostheses in the literal sense, but some had a rather high functionality for those times: they shuffled cards, wrote and drew with a pen, for example. But they had to be "programmed" with mechanical eccentrics, that is, they were automatons. Most likely, the thrust from the stump activated the mechanism and the eccentrics, rotating, carried out their "program". Such prostheses were common until the beginning of the 21st century, when electronic components replaced mechanical ones (with the exception of traction prostheses).
Here's an example of the then prosthetic legs (XVI century):
Well, the story of the knight Goetz von Berlichingen shows that at the beginning of the 16th century there were at least iron prostheses. The paintings of Hieronymus Bosch, again, show that there were the most primitive wooden prostheses that were tied to a cult.