HIP JOINT Flashcards
WK 10 (13 cards)
Functions of the pelvis
- Support and protect pelvic viscera (lower abd organs)
- Provide bony support for birth canal
- Provide area for muscle attachment
- Support weight of head trunk and upper limbs
- Allow for weight transfer:
- From trunk -> lower limb
- Standing -> weight to femurs
- Seated -> weight to ischial tuberosities
Pelvic inlet: (brim)
▪ Pubic crest
▪ Pectineal line
▪ Arcuate line
▪ Sacral alar + promo
* Promontory
Pelvic outlet
▪ Apex of coccyx
▪ Ischial tuberosities
Pubic symphysis (inf ridge)
True VS False Pelvis
True pelvis
- Inf to pelvic inlet
False pelvis
- Sup to pelvic inlet
Differences between male and female pelvis
Pelvic Inlet:
Male: Heart-shaped — narrower and more obstructed.
Female: Wider, oval or round — adapted for childbirth.
Ischial Spines:
Male: Closer together — makes the pelvic cavity narrower.
Female: Further apart — allows a wider birth canal.
Sacral Promontory:
Male: More prominent — reduces pelvic inlet space.
Female: Less prominent — creates a more open pelvic inlet.
Sub-Pubic Angle:
Male: Acute (less than 70–75°) — forms a V-shape.
Female: Obtuse (greater than 80–85°) — forms a U-shape.
Ala (Wings) of Ilium:
Male: Narrower and more upright.
Female: Wider and more flared laterally.
Hip joint - Pubic Symphysis
location
structure
classification
movement
location:
- bw symphyseal surf of pubic bones
structure:
- fibrocart disc
- supported by ligs
classification:
- 2ndary cart joint (symphysis)
movement:
- slightly
* Except in childbirth -> relaxin hormone softens the fibres
Hip Joint - Sacro-iliac Joint
location
classification
articular surfaces
ligaments
Anteriorly: syonvial, plane, non-axial
* Auricular surface of the ilium
* Auricular surface of the sacrum
Posteriorly: fibrous due to I/O ligs
* Tuberosities for the fibrous part of the joint
LIGAMENTS:
Anterior:
- A sacro-liac lig
- Iliolumbar lig
- I/O sacroiliac lig
Posterior:
- P sacroiliac lig
- Sacrotuberous lig
- Sacrospinous lig
Dorsal/Interosseous:
- Interosseous sacroiliac lig
Weight transfer thorugh the pelvis
- Sacrum is bw 2 innominate bones (each made up of the ilium, ischium, and pubis).
- When weight is transferred through the pelvis, it pushes the sacrum inferiorly, creating shear forces—forces acting parallel to the joint surfaces.
- This downward pressure causes the sacrum to become wedged between the ilia.
- Due to the irregular articular surfaces, the joint surfaces interlock, and the sacroiliac ligaments come under tension.
- These ligaments, through their attachments, hold the ilia tightly against the sacrum.
- As a result, the sacroiliac joint becomes self-locking, providing essential pelvic stability during weight transfer.
Movements of the sacroiliac joint due to force
Nutation VS Counternutation
small gliding, slight rotation
Nutation:
- Anteroinferior rotation of the superior sacrum to help absorb shock
- Coccyx shifts P relative to the ilium
- Movement is limited by the wedge shape of the sacrum, irregular joint surfaces and P, I/O, sacrospinous, and sacrotuberous lig’s which are reinforced by surrounding muscles
- Eg. Standing, squatting, childbirth
Counternutation:
- Anterosuperior rotation of the inferior sacrum (body’s response to lift sacrum against gravity)
- Resisted by P sacroiliac lig (supported by the multifidus muscle)
- Eg. During trunk ext
- Eg. Early stance phase of gait
Form closure (passive stability) VS force closure (active stability)
Form closure (passive stability):
what: Anatomical structures that provide pelvic joint stability under high loads
eg:
- Interlocking joint surfaces of SI joint (ridged and irregular → resist movement)
- Wedge-like shape of the sacrum. Gravity and BW push it tighter → ↑ stability
- Ligament tension
Force closure (active stability):
what: Muscles and fascia that provide pelvic joint stability under high loads
eg:
- Muscle group interactions that ↑ joint compression + t/f stability
- Myofascial oblique sling system eg. Glutes, lats, internal obliques
- Overall support for dynamic stability during movement
Movements of the pelvis
Coronal plane
anteroposterior axis
Movements of the pelvis
Sagittal plane
transverse axis
Movements of the Pelvis
Transverse plane
Vertical axis
