The knee-splitter was an ancient form of torture where two planks, each lined with spikes usually varying from 3-20, where put on either side of the victim's knee. The planks where connected by two large screws through the sides holding them in place around the knee. The screws would be twisted, slowly moving the planks closer together and forcing the spikes through the knee. This would rip apart the flesh and, as it got deeper, crush the bones underneath, mutilating the limb and leaving them permanently damaged. Despite the name, the knee-splitter was actually used on any limb it could fit around. This torture device was not always used alone and actually quite often was accompanied by many other punishments such as burning, wedging, denailing, and many others.
The knee-splitter was used during the spanish inquisition as a method to torture prisoners for information. It was also used as a method of punishment.