The femur is the longest and strongest long bone in the human body, and there are individual variations in its length. For adults, the length of the femur is usually 1/4 of their height. The femur is divided into two parts, the upper part has the femoral head, which is associated with the acetabulum. The upper part of the femur is cylindrical, the middle part is trigonous, and the lower part is slightly flattened anteriorly and posteriorly, and the lower part is enlarged in two places, which is connected with the patella. Femur length can also be used to determine fetal development, ultrasound examination after 13 weeks of pregnancy, reference to the standard value of fetal femur length in different periods can be a rough judgment of fetal development, but it should be noted that due to the existence of measurement error, individual differences and other factors, the resulting value is not absolutely accurate, and can only be used as a reference. There is no standardized value for femur length, so if you feel abnormal development, you should consult a doctor and complete relevant examinations to clarify your condition.