Although people often refer to their “hip bones”, the hip is actually one of the major joints of the human body, where the bones of the pelvis and the femur (the thighbone) meet.
The bones of the hip connect in the largest ball and socket joint of the body, formed by the round top of the femur and a coinciding cavity in the bottom of the pelvis. The ball and socket connection allows for some of the widest range of motion, aside from the shoulder – the area can be rotated, lifted, and move both horizontally and vertically, which allows for diverse actions like running, jumping, climbing, and walking.
The hip bears a lot of our body weight: when we walk, the way the stress is distributed over the joint can put as much pressure as five times our body weight. Fortunately, the ball and socket design, combined with the large bones and strong muscles of the thigh and pelvis, help stabilize the hip and carry the weight effectively.
The top of the femur and the socket of the pelvis are both lined with cartilage, a tough tissue about ¼ inch thick that acts as a shock absorber and padding between the bones. The cartilage is kept lubricated by fluid generated in the joint lining; because of this, it remains slippery, allowing the bones to slide easily and painlessly past each other without friction. Cartilage is strong and flexible, but not good at self-repair (unlike other body tissues), so when it becomes worn down due to disease or age, it can be quite painful and affect movement.
The bones that form the hip are held in place by a complex system of muscles, tendons, and ligaments. These tissues, some of the strongest of their kind in the body, support the hip to help prevent dislocation. The gluteals (commonly known as “glutes” or buttocks), the hamstrings on the back of the thigh, the adductors along the inner thigh, the quadriceps on the front of the thigh, and the iliopsoas that runs from the lower back to the upper femur, are all part of this system. Maintaining the strength and flexibility of these muscles and ligaments, through stretching and proper exercise, is one of the best ways to reduce hip pain and prevent injury to the area.