Femur the medial, gives attachment to the fibular collateral ligament of the knee-joint. The femur develops from the limb buds as a result of interactions between the ectoderm and the underlying mesoderm, formation occurs roughly around the fourth week of development. By the sixth week of development, the first hyaline cartilage model of the femur is formed by chondrocytes. Endochondral ossification begins by the end of the embryonic period and primary ossification centers are present in all long bones of the limbs, including the femur, by the 12th week of development. The hindlimb development lags behind forelimb development by 1–2 days.
Arthropod leg with saltatorial legs because the typical leaping mechanism is to straighten the joint between the femur and the tibia, and the femur contains the necessary massive bipennate musculature. The tibia is the fourth section of the typical insect leg. As a rule the tibia of an insect is slender in comparison to the femur, but it generally is at least as long and often longer. Near the distal end there is generally a tibial spur, often two or more. In the Apocrita the tibia of the foreleg bears a large apical spur that fits over a semicircular gap in the