Anatomy of the Hip
The hip joint is made up of two bones: the pelvis and the femur (the thighbone). It is the largest ball-and-socket joint in your body. The “ball” is the rounded end of the femur (also called the femoral head). The “socket” is a concave depression in the lower side of the pelvis (also called the acetabulum). The femoral head fits into the acetabulum to form the hip joint. This anatomy allows for a lot of motion within the joint — for instance, walking, running, and climbing.
The femoral head attaches by way of the femoral neck to the rest of the femur. At the top of the femur, next to the femoral neck, there is another bump on the outside of your hip called the greater trochanter to which muscles attach. Cartilage helps prevent friction between the femoral head and the acetabulum, but hip pain can occur if your cartilage begins to wear down or is damaged.