Stifle joint stifle joint in different species. These sesamoids assist with the smooth movement of tendon/muscle over the joint. The most well-known sesamoid bone is the patella, more commonly known as the 'knee cap'. It is located cranially to the joint and sits in the trochlear groove of the femur. It guides the patellar ligament of the quadriceps over the knee joint to its point of insertion on the tibia. Caudal to the joint, in the dog for example, are the two fabellae, which lie in the two tendons of origin of gastrocnemius. Fourth, there is often a small sesamoid bone in
Femur the bone. Some species of whales, snakes, and other non-walking vertebrates have vestigial femurs. One of the earliest known vertebrates to have a femur is the "eusthenopteron", a prehistoric lobe-finned fish from the Late Devonian period. Structures analogous to the third trochanter are present in mammals, including some primates. In invertebrate zoology the name "femur" appears in arthropodology. The usage is not homologous with that of vertebrate anatomy; the term "femur" simply has been adopted by analogy and refers, where applicable, to the most proximal of (usually) the two longest jointed segments of the legs of the arthropoda. The two