Pelvic Biomechanics

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Questions and Answers

What is one of the basic functions of the pelvis?

to facilitate the movement of the organs involved with bowel and bladder

to support the weight of the upper body and trunk to the femur

to attach muscles of the lower extremity and the trunk (correct)

to increase the diameter of the pelvis during walking

What type of joint is the sacrococcygeal joint?

Synarthrodial joint

Synovial joint

Diathrodial joint

Symphysis (correct)

What is the function of the sacrococcygeal joint?

To attach muscles of the lower extremity and the trunk

To facilitate the movement of the organs involved with bowel and bladder

To increase the anteroposterior diameter of the pelvis during labor and defecation (correct)

To support the weight of the upper body and trunk

What type of joint is the sacroiliac joint in childhood?

Synovial joint Signup and view all the answers

What is the primary function of the sacroiliac joint?

To ensure effective transfer of potentially large loads Signup and view all the answers

What is a primary stabilizer of the sacroiliac joint?

Anterior sacroiliac ligament Signup and view all the answers

What type of movement occurs in the sacroiliac joint?

Small rotational and translational movements Signup and view all the answers

What is a characteristic of the pubic symphysis?

It is firmly bound by a fibrocartilaginous interpubic disc and ligaments Signup and view all the answers

What is nutation defined as in relation to the sacrum and ilium?

The relative anterior tile of the top of the sacrum, relative to the ilium Signup and view all the answers

What is the primary function of nutation and counternutation in the pelvis?

To relieve joint stress and provide stability during load changes Signup and view all the answers

Which of the following muscles helps to stabilize the SIJ?

Erector spinal Signup and view all the answers

What is the movement of the sacrum during retroversion?

The sacrum tilts posteriorly Signup and view all the answers

What is the movement of the ASIS during anteversion?

The ASIS descends Signup and view all the answers

What is the movement of the sacrum during lateral tilt?

The sacrum tilts laterally Signup and view all the answers

Which of the following is NOT a function of nutation and counternutation?

Maintaining posture during standing Signup and view all the answers

What is the movement of the contralateral ASIS during rotation?

The contralateral ASIS moves posteriorly Signup and view all the answers

Study Notes

Pelvic Biomechanics

The pelvis serves as an attachment point for many muscles of the lower extremity and trunk.
It transmits the weight of the upper body and trunk to the ischial tuberosities.
With the help of the muscles and connective tissues of the pelvic floor, the pelvis supports the organs involved in bowel and bladder functions.

Intrinsic Joints of the Pelvis

Sacrococcygeal joint:
- Located between the apex of the sacrum and the base of the coccyx.
- A symphysis joint lined by hyaline cartilage and connected by an interposed fibrous disc.
- Has limited movements of flexion and extension, with one degree of freedom.
- Function: increases the anteroposterior diameter of the pelvis during labor and defecation.
Pubic symphysis:
- Hyaline cartilage lines the surface of the articulation.
- Joint is firmly bound by a fibrocartilaginous interpubic disc and ligaments.
- Allows up to 2 mm of translation and very slight rotation.
Sacroiliac joint (SIJ):
- A modified synarthrodial joint.
- Functions: transitions forces from the pelvic to caudal region, and provides stability for effective transfer of loads.
- Primary stabilizers: anterior sacroiliac, iliolumbar, posterior sacroiliac, and interosseous ligaments.
- Secondary stabilizers: sacrotuberous and sacrospinous ligaments.

Kinematics of the Pelvis: SIJ

Mainly small rotational and translational movements of the SI joints.
Movements based on compression of articular cartilage.
Anthropometric measurements: 1-4 degrees of rotation and 1-2 mm of translation.
Nutation and counternutation:
- Nutation: relative anterior tilt of the top of the sacrum, relative to the ilium.
- Counternutation: relative posterior tilt of the top of the sacrum, relative to the ilium.
Functional considerations of nutation and counternutation:
- Joint stress relief: releases the pelvis from joint stress during support phases.
- Stability during load changes: increases congruency and stability.

Muscles that Stabilize the SIJ

Erector spinal
Lumbar multifidi
Abdominal muscles
Hip extensors
Latissimus dorsi
Iliacus and piriformis

Arthrokinematics of the Pelvis

Anteversion:
- Anterior tilt
- Descent of ASIS
- Ascent of PSIS
- Sacrum: counternutation
- Lumbar extension movement
Retroversion:
- Posterior tilt
- Ascent of ASIS and descent of PSIS
- Sacrum: nutation
- Lumbar flexion movement
Lateral tilt:
- Lateral movement
- Descent of ASIS from one side
- Ascent of contralateral ASIS
- Associated with movements of abduction and adduction
Rotation:
- Anterior movement of ASIS of one side
- Posterior movement of the contralateral ASIS
- Associated with movements during gait

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Description

This quiz covers the basic functions of the pelvis, including its role in muscle attachment, weight transmission, and organ support. It also explores the anatomy of intrinsic and extrinsic joints of the pelvis.