Structure and Function of the Hip Joint

Photo by Wesley Tingey on Unsplash

What is it? The hip is a ball and socket joint where the thigh meets the pelvis.

What bones are involved? The rounded end of the femur in the leg fits inside a socket in the pelvis (i.e., the hip bone) called the acetabulum.

Fancy term for this: cotyloid cavity

How are the bones held in place? Ligaments surround the joint, creating a capsule that keep the bones in place.

Extracapsular ligaments of the hip (front and back). Gray's Anatomy, 1918. Public domain.

There are also intracapsular ligaments that hold the femur within the socket.

Cartoon illustration of the intracapsular ligaments of the hip. Source

How does it move? Cartilage covers the ball of the femur, allowing easy movement within the socket and acting as a shock absorber. The hip joint is also a synovial joint, meaning it is surrounded by a membrane with synovial fluid for lubrication.

Several sets of muscles move the leg at the hip joint, allowing flexion, extension, rotation, abduction, and adduction, including:

• Gluteals

• Quadriceps

• Ilipsoas muscle

• Hip adductors

• Hamstrings

Gross fact: 17 muscles are recognized as muscles that act on the hip joint.

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For more information:

Cleveland Clinic - hip joint

Johns Hopkins Medicine - hip problems