Final Review Flashcards
Three Joint Complex of the pelvis
Sacroiliac joints
Pubic symphysis
Si joints are ____ joints
diarthrotic
True synovial within joint cavity with synovial fluid and joint capsule
L shape of SI joint articulates with
Upper half (leg) articulates at the level of S1 Lower half (foot) articulates at the level of S2-3
Sacral surface segments (S1-3)
Hyaline cartilage (3X thicker than the ilial surface)
Central groove
Wedge shape superior to inferior
S-shape anterior to posterior
Iliac surface from PSIS to PIIS
Fibrocartilage
Central convex ridge
Large rough bony surface posterior and superior to joint for ligamentous attachment (iliac tuberosity)
Development changes of pelvis at birth
Joints underdeveloped, smooth and flat, glide in any direction; stability provided by ligaments
Begin to develop during walking
Development changes of pelvis in the teens
Roughening of surfaces, development of grooves and ridges (male more pronounced than females)
Track bound movement develops (trail and rail)
Development changes in the 3rd through 4th decades
Articular changes in surface anatomy are well established Joint surfaces become more irregular Enlargement of iliac tuberosities and depression Beginning of joint surfaces erosions Possible osteoarthrosis (DJD) on iliac surface (more in males)
Development changes of pelvis at 5th and 6th decades
Joint surfaces become more irregular Each individual joint is unique in its topography to varying degrees (more pronounced in males) Possible osteoarthrosis (DJD) developing on sacral surface and continuing on iliac surface (more in males) Possible development of joint adhesions, osteophytes, and fusion
Changes of pelvis at 70 and above
Interarticular adhesions high prevelance of bony ankyloses (fusion) GENDER DEPENDENT: Male - 27.7% Female - 2.3% AGE DEP[ENDENT: 20-39 years - 5.8% 60-79 years - 31.1% 80+ years - 46.7%
Fusion occurs mainly in the superior part of the joint
Intrinsic SI ligaments
Posterior SI ligaments
Interosseous
Dorsal ligaments
Anterior SI ligaments
Joint capsule
Posterior SI ligaments
Interosseous: massive, major posterior stabilizer
Dorsal ligaments: smaller, not as critical, from sacrum to the PSIS and iliac tuberosity. Limits anterior movement of the sacral base. Dorsal rami run between interosseous and posterior SI ligaments.
Anterior SI ligaments
Thin, thickening of anterior joint capsule
Joint capsule of SI ligament
Well developed anteriorly but not posteriorly
Extrinsic ligaments of pelvis
Sacrotuberous
Sacrospinous
Sacrotuberous ligament
From inferior portion of the sacrum to the ischial tuberosity
Limits posterior movement of the sacral apex
Sacrospinous ligament
From inferior lateral portion of the sacrum to the ischial tuberosity
Limits posterior movement of the sacral apex
Symphysis pubis
Amphiarthrosis
Interpubic fibrocartilagenous disc
Muscles ____ directly act on the SI joint
do not
No muscles cross over the joint
Many MAY influence the mechanical behavior of the joint or respond to stresses applied to it
Muscles which may load the SI joint
Erector spinae QL Psoas Iliacus Piriformis Gluteals
Relationship of muscles to joint dysfunction
Muscles can react to SI stress creating spasms, and trigger points
Abnormal muscle tension may limit overall SI movement leading to joint dysfunction
Innervation of SI joint
Neural elements have been identified in the joint capsule and adjoining ligaments suggesting innervation for pain and proprioception but exact innervation is unknown.
Keystone effect of the pelvis
Sacrum forms the keystone of an arch suspended by strong sacroiliac ligaments
Inferior displacement (would be bad) resisted by the wedge shape of the sacrum
Posterior displacement resisted by SI ligaments
Anterior displacement resisted by SI ligaments and pubic symphysis
Self-locking mechanism of the pelvis
Anatomy of the SI joint promotes stability (form closure) wedge shape of the sacrum interlocking groove (sacrum) and ridge (ilium) S-shaped joint surfaces
Tension in muscles, ligaments, and thorcacolumbar fascia aids in stabilizing the SI joint
creates lateral to0 medial pressure fromt eh ilia to the sacrum, compressing the SI joint
clutch like bracing system
Dynamic biomechanics of pelvis
Transmit forces between lower extremity and axial skeleton
Shock absorber
Slides and pivots to absorb and adapt to forces generated between trunk and lower extremity during locomotion
Decreases stress to lumbar spine and opposite SI joint
SI joint Range of motion
Most agree that it is very small
Egund: up to 2 degrees
Miller: 2.68 degrees flexion, 3.52 degrees extension
Sturesson: 2.5 degrees total motion
Brunner: .54 - 2.83 degrees sacral nutation
Kissling: 1.8-1.9 degrees rotation and translation
Smidt: 5 fresh cadavers in extreme pelvic positions
3-17 degrees, average 7-8 degrees
Pelvic movement general statements
Movement decreases with age
Range is greater in females
Predominant plane of motion is around the x-axis in the semi-sagittal plane
Axis of rotation is speculative but most commonly placed posterior to the joint around the iliac tuberosity
Motion is coupled and dependent to some degree on joint separation
Motion is not uniform between individuals
Developmental changes in surface architecture
Movement is greatest during locomotion
Illi’s model of locomotion
Reciprocal motion between ilium and sacrum
Flexion of hip and ilium (posterior inferior movement of the PSIS) is accompanied by ipsilateral anterior inferior movement of the sacral base (SI flexion)
