The Pelvis and Pelvic Ring

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Questions and Answers

Where is the sacroiliac joint located?

Just posterior to the posterior superior iliac spine of the ilium

Just anterior to the posterior superior iliac spine of the ilium (correct)

Near the public symphysis

At the lumbar vertebrae

What is the shape of the articular surface of the sacroiliac joint?

Triangular

Circular

Rectangular

Semicircular, boomerang-shaped (correct)

What type of cartilage covers the sacral surface of the joint?

Hyaline cartilage (correct)

Fibrocartilage

Articular cartilage

Elastic cartilage

What is the purpose of the reciprocally contoured elevations and depressions in the joint?

To increase friction in the joint Signup and view all the answers

What type of joint is the sacroiliac joint?

Hybrid joint Signup and view all the answers

What limits anterior motion in the sacroiliac joint?

Interrosseous S-I ligaments Signup and view all the answers

How much motion is permitted in the sacroiliac joints?

A small amount of motion Signup and view all the answers

What is the primary function of the sacroiliac joint?

Stability Signup and view all the answers

What is the role of the pelvis in the skeletal system?

Transferring body weight between the trunk and femurs Signup and view all the answers

What type of cartilage covers the iliac surface of the joint?

Fibrocartilage Signup and view all the answers

What is the name of the joint that adds structural stability to the pelvic ring?

Pubic symphysis joint Signup and view all the answers

What is the relationship between the thickness of the sacral and iliac cartilage?

The sacral cartilage is thicker than the iliac cartilage Signup and view all the answers

What is the role of the sacrum in the pelvis?

Acting as a keystone Signup and view all the answers

What is the name of the three bones that make up each hemipelvis?

Ilium, ischium, and pubis Signup and view all the answers

What is the main component of the load (force) transition in the pelvis?

The pelvic ring Signup and view all the answers

What is the shape of the sacroiliac joint?

Wedge-shaped Signup and view all the answers

What is the function of the pelvis in relation to the spine and lower limb?

Connecting the spine and the lower limb Signup and view all the answers

What is the role of the pelvic ring?

Transferring body weight bidirectionally Signup and view all the answers

What is one of the essential functions of the SI joint?

Weight distribution and maintaining balance Signup and view all the answers

What is the primary role of the SI joint?

Maintaining stability to the pelvis and lower back Signup and view all the answers

What is the function of the Interosseus ligament?

Stabilizing the SI joint Signup and view all the answers

What type of fibers make up the Interosseus ligament?

Short and dense fibers Signup and view all the answers

What is the function of the sacroiliac ligaments?

Stabilizing the SI joint Signup and view all the answers

What is the secondary function of the Iliolumbar ligament?

Stabilizing the lumbosacral joint Signup and view all the answers

Which ligament is responsible for preventing anterior movement?

Anterior sacroiliac ligament Signup and view all the answers

What is the function of the SI joint in terms of physical activities?

Reducing the impact of physical activities Signup and view all the answers

What is unique about the SI joint in comparison to other joints?

It is one of the strongest joints in the body Signup and view all the answers

Study Notes

Pelvis and Sacroiliac Joints

The sacroiliac joints mark the transition between the axial skeleton and the lower appendicular skeleton.
The SI joint is located just anterior to the posterior superior iliac spine of the ilium.

Structure of the Sacroiliac Joints

The joint consists of a relatively rigid articulation between the auricular surface of the sacrum and the matching auricular surface of the iliac bone.
The articular surface of the joint has a semicircular, boomerang shape, with the open angle of the "boomerang" facing posteriorly.
Articular cartilage covers both bony auricular surfaces of the joint, with the sacral surface composed of hyaline cartilage and the iliac surface composed of fibrocartilage.
The thickness of the sacral cartilage is greater than that of the iliac cartilage.

Characteristics of the Sacroiliac Joints

A mature sacroiliac joint possesses numerous, reciprocally contoured elevations and depressions, etched within the subchondral bone and articular cartilage.
These roughened areas increase the coefficient of friction within the joint, enhancing the resistance against vertical shear between the joint surfaces.
The SI joint is a hybrid joint, with one part being a synovial joint (the lower part) and the other a fibrous joint (the upper part).
The joint is held in place by tough Interrosseous S-I ligaments, which help limit anterior motion.

Functions of the Sacroiliac Joints

The SIJs permit a small amount of motion that varies among individuals.
The main functions of the SI joint are:
- Weight Distribution: weight-bearing function is essential for maintaining balance and stability.
- Shock Absorption: reduces the impact of physical activities on the spine and other joints.
- Limiting Mobility: allows slight movements, its primary role is to provide stability to the pelvis and lower back.

Ligaments That Stabilize the SI Joint

Primary ligaments:
- Interosseus ligament (stabilizes SIJ)
- Anterior sacrioiliac ligament
- Posterior sacroiliac ligaments
  - Short posterior sacroiliac ligament
  - Long posterior sacroiliac ligament
Secondary ligaments:
- Indirectly associated with the SI joint
  - Sacrotuberous ligament
  - Sacrospinous ligament
  - Iliolumbar ligament (stabilizer of the lumbosacral joint)

Additional Notes

The sacroiliac ligaments as a whole extend from the iliac crests to attach to the tubercles of the first four sacral vertebrae.
The Interosseus ligament consists of a set of very dense and short fibers that fill most of the gap along the posterior and superior margins of the joint.
The Interosseus ligament is the strongest ligament of the sacroiliac joint, rigidly binding the sacrum with the ilium.

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Description

Quiz on the anatomy and function of the pelvis, including joint structure, ligamentous support, kinematics, and stability. Based on Neumann and Kapandji's works.