Movement Science Week 4 - SI Joint Review

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is one of the primary functions of the sacroiliac joint?

Acts as a shock absorber during running

Facilitates respiratory movements

Connects the foot to the leg

Serves as the interface between the axial and appendicular skeletons (correct)

Where is the sacroiliac joint located?

Between the sacrum and the ilium (correct)

Between the ribs and the sternum

At the junction of the hip and thigh

In the lumbar region of the spine

What anatomical feature can be palpated to approximate the location of the sacroiliac joint?

The sacral canal

The PSIS (posterior superior iliac spine) (correct)

The coccyx

The iliac crest

What percentage of chronic low back pain cases is the sacroiliac joint estimated to be responsible for?

25% Signup and view all the answers

Why is the sacroiliac joint often overlooked in clinical assessments?

It is located deep within the pelvis Signup and view all the answers

What type of activities can cause unilateral torsion, impacting the sacroiliac joint?

Running and jumping off one leg Signup and view all the answers

What best describes the relationship between the sacroiliac joint and sports injuries?

It can contribute to low back pain in athletes Signup and view all the answers

What skeletal structures articulate at the sacroiliac joint?

The sacrum and the ilium Signup and view all the answers

What do the terms nutation and counternutation refer to in relation to the sacrum?

The relative anterior and posterior tilting of the sacrum. Signup and view all the answers

What is one primary function of the sacroiliac (SI) joint?

Providing stress relief and stability. Signup and view all the answers

Why is nutation particularly important during pregnancy?

It enlarges the pelvic outlet for childbirth. Signup and view all the answers

What happens to the sacral promontory during nutation?

It tilts anteriorly. Signup and view all the answers

What role do gravity and ground reaction forces play in the stability of the SI joint?

They act through moment arms to enhance joint stability. Signup and view all the answers

What does the close-packed position of the SI joint indicate?

It is associated with the highest stability. Signup and view all the answers

How does the SI joint contribute to stress relief during running?

By facilitating the torsion created by descending and ascending forces. Signup and view all the answers

Study Notes

Sacroiliac (SI) Joint: Osteology and Function

The SI joint is the primary connection between the axial (head, trunk) and appendicular (extremities) skeletons, specifically the lower extremity.
It's located between the ileum (part of the pelvis) and the sacrum. The joint itself is not directly palpable, but can be approximated by locating the posterior superior iliac spine (PSIS) – a bony protrusion felt easily while marching in place – and moving slightly anteriorly.
Chronic low back pain originates from the SI joint in approximately 25% of cases. Repetitive unilateral torsion, common in activities like running and jumping, can exacerbate pain in this area.

Pelvic Ring and SI Joint's Role

The pelvic ring encompasses the sacrum, two SI joints, the ilium, pubis, ischium (sit bones), and the pubic symphysis. The sacrum acts as the keystone of this ring.
The SI joint functions as an area of pressure release within this ring structure.

SI Joint Motion: Nutation and Counternutation

Movement at the SI joint involves nutation and counternutation.
Nutation refers to the anterior tilt of the sacral promontory (top of the sacrum) relative to the innominate (half of the pelvis). This can be sacral tilt or posterior iliac tilt.
Counternutation is the opposite movement: posterior movement of the sacral promontory and anterior movement of the ilium.

Functional Considerations: Stress Relief and Stability

The SI joint's primary functions are stress relief and stability.
Stress Relief: The SI joint alleviates stress during gait/running by helping to manage the torsion created by descending gravity and ascending ground reaction forces. It also aids in stress relief during pregnancy by increasing pelvic outlet size via nutation, facilitating childbirth.
Stability: The SI joint enhances stability, particularly during standing wherein gravity's downward force and the joint reaction force through the acetabulum (hip socket) create a moment arm that leads to nutation. Nutation represents the close-packed position of the SI joint, maximizing stability.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the anatomy and function of the sacroiliac joint, which serves as a key connection between the axial and appendicular skeletons. Understand its role in the pelvic ring and its significance in conditions like chronic low back pain. Test your knowledge on this crucial yet often overlooked joint.