The answer is femur because of the protruding ball that fits into the socket of the pelvis. The femur is the lone bone in the thigh in which femur encounter medially in the direction of the knees where they eloquent with the proximal ends of the tibiae. The angle of conjunction of the femora is a major factor in defining the femoral tibial angle. Human females have broader pelvic bones affecting their femora to unite more than in males. In the situation genu valgum which the femurs unite so much that the knees touch one another. The opposite extreme is genu varum and in the over-all population of people deprived of either valgum or genu varum the femoral tibial angle is about 175 degrees.
