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beginnerSource-checked11 min read

The Pelvis & Hips: An Overview

The bony ring and ball-and-socket joint that connect the spine to the legs and transfer force between them.

Before this: Fundamental Movement Terms

You will be able to

  • Describe the hip joint as a ball-and-socket joint and name its bones.
  • Identify the iliopsoas as the primary hip flexor.
  • Explain why the pelvis is a central link between the upper and lower body.
Simplified front view of the pelvis showing the wing-shaped hip bones meeting at the pubic symphysis, the ball-and-socket hip joint where each femur meets the acetabulum, and the iliopsoas running from the lower spine across the front of the hip to the femur.
Pelvis & hips — hip bone, hip joint, and iliopsoas (simplified). A beginner-level schematic of the pelvis's bony ring, the hip joint, and the iliopsoas hip-flexor muscle.
Illustration: Anatomy Learning Platform (original) · CC0-1.0 (public domain dedication)

⚠ Safety note

Sharp groin/hip pain, joint locking or catching, or pain that prevents weight-bearing needs medical evaluation, not exercise. A trainer coaches hip mobility and strength work; they do not diagnose hip joint pathology.

A bony ring with a deep socket

The pelvis is formed by the two hip bones joined to the sacrum behind. Each hip bone contains the acetabulum — a deep cup that, together with the rounded head of the femur, forms the hip joint: a stable ball-and-socket joint built for both mobility and heavy load-bearing.

The primary hip flexor

The iliopsoas — really two muscles (psoas major and iliacus) working as one — is the main muscle that lifts your thigh toward your chest. Because the psoas major attaches directly onto the lumbar spine, hip flexor tightness and low-back posture are closely linked.

The pelvis as a link

Sitting between the spine and the legs, the pelvis transmits force in both directions: up from the ground through the legs, and down from the trunk during lifting. Good hip mobility lets that transfer happen efficiently, which is why hip-focused mobility work often appears alongside core and low-back training.

Sources for this lesson

“The hip joint is a ball-and-socket joint between the femoral head and the acetabulum; the iliopsoas is the primary hip flexor.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 7.5 The Pelvis; Ch. 11.6

Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19

Take the quiz (4 questions)Explore the Pelvis & Hips

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