Week 5 content Flashcards
Describe the articulation of the sacroiliac joint.
Synovial joint, but only sacrum is lined with hyaline cartilage, and ilium is covered in fibrous cartilage
Both sacrum and ilium are irregularly shaped to help the bones interlock with each other
Strong joint capsule and the strongest ligaments in the body support it
Ear-shaped articulation surfaces
Less than 4 degrees of rotation
Compression helps to prevent shear
Name the ligaments of the SI joint.
Interosseus sacroiliac ligaments Posterior sacroiliac ligaments Anterior sacroiliac ligaments Iliolumbar ligament Sacrotuberous ligament Sacrospinous ligament
Describe the interosseus sacroiliac ligaments.
Massive, strong ligaments that unite the sacral and iliac tuberosities
Describe the posterior SI ligaments.
Composed of short and long fibers that connect the sacrum and ilium posteriorly. Blends with the sacrotuberous ligament. AKA long dorsal SI ligament
Most superficially placed
Describe the anterior SI ligaments.
Transverse fibers that support the anterior and inferior portion of the SI joint
Completes the joint capsule anteriorly
Describe the iliolumbar ligament.
Accessory ligament of the SI joint. Supports the L5-S1 joint
Describe the sacrotuberous ligament.
Helps support the SI joint by preventing nutation of the sacrum.
VERY important ligament in SI joint, works with sacrospinous
Longer, more posteriorly, exteriorly, and superficially placed compared to sacrospinous.
Describe the sacrospinous ligament.
Helps support SI joint by preventing nutation
VERY important for SI joint, works with sacrotuberous
Shorter and more anteriorly + deeply placed compared to sacrotuberous
Describe how the SI joint overcomes torque forces.
Weight of body coming down through the spine rotates sacrum anteriorly (nutation)
Ground reaction force through femur rotates ilium posteriorly, which further contributes to nutation.
Creates a locking mechanism to overcome torque
Describe how the SI joint overcomes shear.
Form and force closure - combination of angled joint surface to provide some form closure, and muscular activity of the LE to provide some force closure to counteract weight of body coming down through the spine
SI joint subject to shear forces d/t the vertical orientation of the joint facets, weight-bearing of the body, and gravity
T/F: SI dysfunction is usually a result of impaired load transfer through the SI joints.
True
Nutation of the sacrum is restrained by which ligament?
Sacrotuberous ligament
further enhanced by the action of biceps femoris attachment to ischial tuberosity
Counternutation of the sacrum is restrained by what ligament?
Long dorsal SI ligament
further enhanced by action of the latissimus dorsi through its attachment via the TLF
When is load transfer through the pelvic girdle most effective?
When sacrum is nutated or tilted forward at its superior aspect
What muscles contribute to compression of the SI joint anteriorly and posteriorly?
Latissimus dorsi via the TLF and its contralateral gluteus maximus (posteriorly)
Internal and external obliques (anteriorly)
Describe the classification and articulation of the hip joint.
Synovial joint - ball and socket
Articulation of the head of the femur and the acetabulum of the ox coxae
Describe the acetabulum.
Deepened by the acetabular labrum, which attaches to the bony rim and the transverse acetabular ligament, which spans the acetabular notch, creating the acetabular foramen, which provides passage of blood vessels and nerves to the joint cavity
Describe the femur as it relates to the hip joint.
Attached to the transverse acetabular ligament and the acetabular labrum via the ligament of the head of the femur (AKA ligamentum teres femoris)
Attachment of the ligament is marked on the femur by a small depression called the fovea capitis, where there is no articular cartilage.
Describe how the hip joint ligaments aid in compression of the head of the femur into the acetabulum.
The iliofemoral, pubofemoral, and ischiofemoral ligaments all restrain hip extension by becoming taut in extension, winding around the femur and compressing it into the acetabulum
Loose-packed joint position: ligaments are straight and loose
Close-packed: ligaments are wound and taut in hip extension
Describe the angle of Wiberg.
Shows how much of the acetabular rim surrounds the head of the femur
Made with the line of vertical weight bearing the the plane of the acetabular rim
Normally 25-40 degrees
Name the ligaments of the hip joint capsule.
Iliofemoral ligament (Y ligament)
Ischiofemoral ligament
Pubofemoral ligament
Zona orbicularis
Describe the iliofemoral ligament.
AKA the Y ligament
Extends from AIIS and acetabular rim to the intertrochanteric line
Taut in extension and prevents hyperextension of the hip in standing.
Describe the ischiofemoral ligament.
Extends from acetabulum posteriorly and spirals superolaterally to the neck of the femur and greater trochanter.
Becomes taut in extension and helps prevent hyperextension
Describe the pubofemoral ligament.
Extends from the pubic part of the acetabulum and superior ramus to the lower part of the intertrochanteric line.
It is taut in extension and abduction and helps
prevent excessive abduction
Describe the zona orbicularis.
Capsular fibers that encircle the neck of the femur, cinching down the capsule around the neck of the femur
Thickening of joint capsule that creates an O-ring around the neck