Hip
Ball-and-socket joint connecting pelvis and femur.
The hip, or coxa in medical terminology, refers to either an anatomical region or a joint on the outer side of the pelvis. It is a ball-and-socket joint between the pelvic acetabulum and the femoral head, supporting the weight of the torso in static and dynamic postures and playing a key role in balance and pelvic inclination.
- type
- Anatomical structure
- location
- Lateral side of the pelvis, inferior to iliac crest, lateral to obturator foramen
- components
- Acetabulum, femoral head, acetabular labrum, ligaments (iliofemoral, ischiofemoral, pubofemoral)
- function
- Support torso weight, retain balance, maintain pelvic inclination angle
- range_of_motion
- Second largest range of movement after the shoulder
Lore & Background
The hip joint, scientifically called the acetabulofemoral joint, is formed by the articulation of the rounded head of the femur and the cup-like acetabulum of the pelvis. The acetabulum is formed at the union of the ilium, pubis, and ischium, with the triradiate cartilage fusing definitively at ages 14–16. The joint is a special type of spheroidal joint where the femoral head, with an average radius of curvature of 2.5 cm, is largely contained within the acetabulum, deepened by the acetabular labrum.
Reader's Guide
The hip is significant as the primary connection between the lower limb and the axial skeleton, enabling weight-bearing and locomotion. Its structure includes a strong fibrous capsule and four ligaments—three extracapsular (iliofemoral, ischiofemoral, pubofemoral) and one intracapsular—that prevent excessive movement. The hip's articular angles, such as the acetabular angle and Wiberg's centre-edge angle, are used clinically to assess development and pathology. Pain in the hip can arise from nervous, osteoarthritic, infectious, traumatic, and genetic causes. The femoral neck is often prone to fracture in the elderly due to osteoporosis.
Did You Know?
- The acetabular labrum is horse-shoe shaped and extends the joint beyond the equator.
- The hip joint has the second largest range of movement of any joint, after the shoulder.
Frequently Asked Questions
What is Hip in the Musculoskeletal System?
Hip is entry 1-24 in the series, representing the ball-and-socket joint that links the pelvis to the femur on the outer side of the body. It sits below the iliac crest and lateral to the obturator foramen.
What are Hip's components?
Hip is built from the acetabulum, femoral head, acetabular labrum, and three reinforcing ligaments: the iliofemoral, ischiofemoral, and pubofemoral. Together these structures allow smooth rotation while keeping the joint stable.
What is Hip's primary role?
Hip bears the full weight of the upper body whether you are standing still or in motion. It also helps you stay balanced and keeps your pelvis tilted at the correct angle.
How does Hip's range of motion compare to other joints?
Hip ranks as the second most mobile joint in the body, trailing only the shoulder. This wide range of movement is what makes activities like walking, running, and kicking possible.
Why is Hip important to the overall system?
Without Hip, the pelvis could not transfer load from the torso down into the legs, making weight-bearing and locomotion impossible. It is the critical pivot point that connects the upper and lower halves of the musculoskeletal framework.
More in Musculoskeletal System 1-24
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