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 patella 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 body.
Even though Supergirl (Kara Zor-El) was 12 when her parents sent her to Earth to escape Krypton to look after her baby cousin Superman (Kal-El), her pod was knocked off course and stuck in space and she was effectively stuck in time. By the time her pod reached planet earth, Kal-El had already grown up and become Superman while she was still young.