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
Douzhanopterus then the fourth, which is still about 80% the length of the second. Fused entirely to the sacrum is the pelvic girdle. The portion of the pelvic girdle in front of the femoral joint appears to consist of two unfused prepubes, which are longer than they are wide. The femur is slightly curved, and the femoral head and neck form an angle of about 150° with the shaft. On the lower leg, the relatively straight tibia is about 180% the length of the femur; the fibula, which is about 45% the length of the tibia, is fused to it at