Bipedalism is the ability to stand and walk entirely on two feet. Bipedalism is marked by several adaptive skeletal changes along with certain costs. The most spectacular alterations to support body weight and maintain balance are in spine, the pelvis, the skull and the feet. On the other hand, overloaded low back and lower extremity joints during bipedal locomotion cause knee and back pain later in life. In females, to walk upright may be difficult and painful to carry as well as deliver a baby with a large brain. Other disadvantages of bipedal gait are longer motor learning period and inability to ambulate when one leg is injured. Morphological adaptations that are crucial to support and enable this new form of locomotion include: a more inferiorly placed foramen magnum, larger femoral head, increased femoral neck length, anteroposteriorly elongated condyles of the femur, the knee positioned in slight valgus at knees due to bicondylar angle, shorter big toe, and a higher foot arch.
