A method and device for performing an accurate cutting operation near the knee joint of a leg (25;154;192) of a slaughtered animal, in particular a bird, the device comprising mechanical means, such as conveying elements and guides, for handling the leg, and cutting means, such as rotary or stationary knives for performing the cutting operation, e.g. for making an incision prior to scraping off meat of a bone or for cutting through the leg. With the device, the desired cutting accuracy is obtained by using mechanical positioning means which operate on the kneecap of the leg, which is preferably bended in the knee joint in its natural bending direction by bending means. The positioning means may comprise one or more supporting elements (94;164;216,218) with a stop edge, which can be moved along the thigh of the leg to against the kneecap.