The sacrum is a shield-shaped bony structure that is located at the base of the lumbar vertebrae and that is connected to the pelvis. The sacrum forms the posterior pelvic wall and strengthens and stabilizes the pelvis.

The fibula is a long bone in the lower extremity that is positioned on the lateral side of the tibia. The fibula is much smaller and thinner than the tibia. It is located just behind the tibial head at the knee joint and then runs down the lateral aspect of the leg until it reaches the ankle joint.

The tibia is one of two bones that comprise the leg.[1] As the weight-bearing bone, it is significantly larger and stronger than its counterpart, the fibula. The tibia forms the knee joint proximally with the femur and forms the ankle joint distally with the fibula and talus.

The linea aspera is the rough, longitudinal crest on the posterior surface of the femoral shaft. Most orthopedic surgeons depend on the linea aspera as an intraoperative landmark identifying the true posterior aspect of the femur.

The adult os coxae, or hip bone, is formed by the fusion of the ilium, the ischium, and the pubis, which occurs by the end of the teenage years. The 2 hip bones form the bony pelvis, along with the sacrum and the coccyx, and are united anteriorly by the pubic symphysis.

The tibia is one of two bones that comprise the leg.[1] As the weight-bearing bone, it is significantly larger and stronger than its counterpart, the fibula. The tibia forms the knee joint proximally with the femur and forms the ankle joint distally with the fibula and talus.