HIP ANATOMY

What is the hip made of?

The hip is the area where the thigh bone meets the pelvis, forming a ball and socket joint. The hip's function is to connect the lower body with the pelvis. The femur (thigh bone) is the lengthiest bone in the human body. On each side of the hip bone lies the acetabulum, also known as the socket that makes up the ball-and-socket joint. The surface of the acetabulum is a part of the pelvis that is replaced in hip replacement surgery.

The hip consists of two parts which help maintain weight-bearing balance. The first part is the ball of the hip, situated at the top of the thigh bone. The second part of the round socket rests in the pelvis. In order to keep everything connected to each other, the body uses bands of flexible tissue called ligaments to hold the structure together and keep the hip steady and stable. The cartilage in the hip joint has a thin layer of lubricated tissue called articular cartilage, which helps the hip bones move freely.

The hip also has several fluid-filled pockets that help prevent the bones from rubbing against each other, which may result in hip pain. The synovial membrane is a fine layer of connective tissue that lines the joint’s cavities, the fluid-filled sacs between the tendons and bones (called the bursae), and tendon sheaths. The primary function of the synovial membrane is to produce synovial fluid (a lubricant) that helps prevent joints from colliding.

Basic components of a hip joint:

The hip joint, also called the Acetabulofemoral joint, consists of the following components:

• Hip bones include the femur and the pelvic bones.
• Hip articular cartilage helps decrease friction between the bones, allowing the joint to glide smoothly.
• Hip muscles support the hip joint enabling movement.
• Hip ligaments and tendons are tough, fibrous tissues that help bind the bones and muscles together.
• Synovial membrane and fluid encapsulate and lubricate the hip joint.

The ball-and-socket construction allows the following three flexibilities:

• Hip abduction and adduction enable movement of the leg out to the side (called the abduction motion) and inward toward the other leg (called the adduction motion).
• Hip flexion and extension involve moving the leg back and forth.
• Rotation – internal rotation occurs when you point your toes inward or outward, which is external rotation. Rotation also occurs when moving the leg in the direction of the toe.