What is the hip joint? Why is it so important? Today, we take a dive into hip anatomy, physiology, and what makes it such an important joint within the body.

The hip joint is an important joint complex composed of the femoral head, which inserts into the acetabulum of the pelvic bone; hence why the hip is also called the femoroacetabular joint. The ligamentum teres is what connects the femoral head into the cavity of the acetabulum. The hip is a very stable and sturdy joint, as it is surrounded by multiple ligaments; from the front, the iliofemoral ligament (also known as the Y-ligament), connects the femur to the front of the ilium at the anterior inferior iliac spine. The pubofemoral ligament connects the femur to the superior ramus of the pubic bone. From behind, the ischiofemoral ligament attaches the femur to the ischium of the pelvis. Each of these ligaments prevents excessive movements that are likely to cause injury, such as hyperflexion or hyperextension. The muscles that act on the hip joint will be discussed in the next section.

Although the hip is a stable joint due to its ligamentous attachments, the hip is also very mobile. The hip is classified as a ball-and-socket joint, meaning it provides the greatest capacity for movement; the hip is able to move within all planes of motion. The hip joint is the second most mobile joint complex within the body, second only to the shoulder (or glenohumeral joint). The movements of the hip include forward and backward movements (flexion and extension), side-to-side movements (abduction – move hip outward, and adduction – move hip inward), and rotational movements (internal and external rotation). The major muscles that act on the hip include the iliopsoas (hip flexion), gluteus maximus (hip extension), gluteus medius/minimus (hip abduction and internal rotation), piriformis, gemelli, obturator internus, quadratus femoris (external rotation), adductors longus, brevis, magnus, and gracilis (hip adduction).

Note: this is not an all-inclusive list of muscles and their actions on the hip joint.

The hip joint is incredibly important due to its stability, mobility, and its ability to withstand great loads placed upon it. As previously stated, the hip is a stable, sturdy joint within the body, despite its ability to produce lots of movement. The hip joint is loaded throughout the day, mostly with walking, running, and standing. With walking/gait cycle, hip loading alternates as one foot is placed on the ground while the other is taking a step forward. Lifts completed from a standing position will also add increased load to the hip joints. Proper hip joint biomechanics are extremely helpful when it comes to lower body exercise technique. Exercisers should dedicate a warm-up to the hips prior to lower body training days to address any and all mobility and/or stability deficits.