Femur Femur The femur (, pl. "femurs" or "femora" ) or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia and kneecap forming the knee joint. By most measures the femur is the strongest bone in the body. The femur is also the longest bone in the human body. The femur is the only bone in the upper leg. The two femurs converge medially toward the knees, where they articulate
Vertical clinging and leaping phalangeal index, low intermembral index, femurs with cylindrical head and high, narrow patellar grooves, and fused fibula and tibia. The high phalangeal index is the elongation of the phalangeal finger bones, which helps vertical clingers who require increased prehensile power in their hands to support their large bulk. The low intermebral index is the total length of the humerus and radius in percentage of total length of the femur and tibia. The features of the femur is part of an evolution of elongated femurs that helps the primates' extreme range of flexion and extension, which allows them to perform their