Biomechanics of Hip and Pelvis Produced by Phil Austin
Phil Austin
Introduction to Hip Joint
Articulation of the acetabulum of the pelvis and the head of femur The 2 segments form a ball and socket joint with 3° of freedom Flex / ext Abd / Add Med / Lat rotation Phil Austin
Primary Function
To Support weight of head, arms and trunk (HAT) During static erect posture and dynamic postures (e.g. running). Primarily structured to serve its weight bearing function (supports ⅔ body weight) Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Phil Austin
Structure
Full ossification occurs at 20 – 25 years The acetabulum appears to be a hemisphere, BUT only the upper margin has a true circular contour.
The “roundness” decreases with age.
Only the upper horse shoe shaped area is articular.
Phil Austin
Acetabular Fossa – Fossa – non art articu icular lar.. Contains fibro-elastic fat covered with synovial membrane
Netter F, Atlas of Human Anatomy, 2nd ed.
Proximal Articular Surface Located at lateral aspect of innominate. Bones form the acetabulum Ilium (2/5) Ischium (2/5) Pubis (1/5)
Acetabular notch – spanned by fibrous band (transverse acetabular ligament) T.A.L. This connects the 2 ends of the horse shoe. Netter F, Atlas of Human Anatomy, 2nd ed
Creates a fibro-osseous tunnel through which blood vessels can pass to the deepest part of the acetabulum.
Central Edge Angle (CE) In Males ≅ 38 ° In Females ≅ 35 ° Smaller Smal ler CE CE angle angle – may result in diminished coverage of the head of femur.
∴ ↑ risk of superior dislocation.
CE angle increases with age have ↓ coverage over the head of the femur ∴Children
= ↓ coverage over the head of femur compared to adults Congenital dislocation is most common at the hip joint due to
↓CE angle. Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Acetabular Anteversion Anteversion..
Anterior orientation – “Angle of acetabular anteverision”
Men – 18.5 ° Women – 21.5 °
NB – Kapandji cites values of 30 - 40 °
∴ ↑ Anteversion = ↓ joint stability + ↑ chance anterior dislocation. Phil Austin
Acetabular Labrum Covers entire periphery of acetabulum. Deepens the “socket” Increases concavity through its triangular shape Grasps the head of femur to maintain contact with acetabulum. Transverse acetabular ligament – considered part of the labrum (BUT contains no cartilage cells)
Netter F, Atlas of Human Anatomy, 2nd ed
Structure of Distal Articular Surface
Head of femur – – fairly rounded hyaline cartilage covered – slightly larger than a true hemisphere. The radius of the femoral head is smaller in females when compared to the dimensions of the pelvis. Levangie PK, Norkin CC. Joint Structure and Function, Function, aa Comprehe Comprehensive Analysis. 3rd ed 2001
Phil Austin
Ligamentum Teres - Ma Main in Fu Func ncti tion on – ac actt as as a channel for secondary blood supply from the obturator artery and nerves. Blood supply via this is greater in childhood Sclerosis of the ligament in elderly. ∴ secondary supply cannot back up primary retinacular supply Absence increases risk of avascular necrosis to head with femoral neck trauma.
Fovea – Inferi Inferior or to most medial medial point point on femoral femoral head. Attachment point of the ligament of head of femur is attached.(Ligamentum attached.(Ligament um Teres) Femoral head Femoral head – atta attached ched to femoral femoral neck; neck; the neck neck is attached to shaft between the greater and lesser trochanter.
Netter F, Atlas of Human Anatomy, 2nd ed
Angulation of Femur
Femoral head faces medially, superiorly and anteriorly. Frontal plane
– ∠ of inclination
Axis of femoral head, neck and longitudinal axis of shaft
Transverse plane - ∠ of torsion Axis of femoral head and neck and an axis through the distal femoral condyles. Phil Austin
Embryonic Development.
Early stages – both ↑ and ↓ extremity buds project laterally from body (full abduction). abduction). At 7 / 8 weeks gestation, adduction of the joints begin. By the end of week 8, the foetal position has been achieved. Phil Austin
150 ° in infancy. 125 ° in adults. 120 ° in the elderly The ∠ varies among individuals and sexes Female = ↓ due to greater width of female pelvis. Singleton. HC LeVeau BF: Stability & Stress, A review. Phys Ther 55, 957-973, 1975
Normal ∠ of inclination inclination – the greater greater trochanter trochanter lies lies at the level level of the centre of the femoral head. Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
A pathological increase between neck and shaft – COXA VALGA Decrease – COXA VARA Phil Austin
Angle of Torsion of Femur
Best viewed by looking down the length of the femur. This angle reflects the twist in the bone that occurs during foetal development. Normal torsion – anterior. This is due to the knee being aligned in a frontal plane. Allowing the knee to flex and extend in a sagittal plane.
Phil Austin
Angle of Torsion of Femur
Each structural deviation needs careful consideration as to the impact on the hip joint AND function of joints both proximal and distal to it. Anteversion can cause significant dysfunction to both knee and foot.
Both angles of inclination and torsion are
Properties of the Femur and exist independently independ ently to the hip joint. Phil Austin
Pathological Anteversion
Age (y)
Anteversion (in degrees)
.
Birth irth - 1 y
30 - 50
2
30
3-5
25
6 -12
20
12 -15
17
16 - 20
11
20
8
Pathological Retroversion
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Signs & Symptoms Anteversion
Retroversion
Toeing in Squinting patellae Subtalar pronation Medial tibial torsion Medial fe femoral to torsion
Toeing out Subtalar supination Lateral tibial torsion lateral ti tibial torsion
www.clinicalsportsmedicine.com/chapters/24b.htm
Phil Austin
Articular Congrue Congruence nce
Considered congruent BUT - Significantly more articular surface on the head of femur than on the acetabulum. In standing position – head is exposed anteriorly and superiorly. ∴ Angle of torsion is poorly matched to anterior orientation of acetabulum. Levangie PK, Norkin CC. Joint Struct ure Comprehensive Analysis. 3rd ed 2001 Structur e and Function, a Comprehensive
Phil Austin
Articular Congrue Congruence nce
Coxa Valga, anteversion or a shallow acetabulum results with increased :
Articular exposure of the femoral head
Less congruence
Reduced stability In an a neutral standing position.
Increased articular contact can be achieved with flexion, abduction and slight lateral rotation. Phil Austin
Contact of the femoral head on the acetabulum Increases during flexion and abduction b) = maximum articular contact of femoral head
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Articular Congrue Congruence nce
The Acetabular fossa may set up a partial vacuum – so atmospheric pressure may contribute to stability. Maintaining contact of the 2 articulating surfaces. Atmospheric pressure plays a stronger role in stabilization than the capsuloligamentous structures (Wingstrand H et al, Intracapsular and atmospheric pressure in the the dynamics and stability of the hip. Acta Orthop Scand, 61: 231231-235. 1990)
Phil Austin
Hip Joint Capsule
Strong and Dense
Attached to entire periphery of bony acetabulum.
Covers femoral neck and head
Gtr / Lssr trochanter – – Extra articular.
2 sets of fibres Superficial Superficial longitudinal fibres - Retinacular Deeper circular fibres – Zona Orbicularis (collar like) Phil Austin
Iliofemoral lig - Re Refer ferred red to as as – Y liga ligamen mentt – str stron onger ger / thickest of all hip ligaments. Bands of ilio pubo / femoral femoral ligs ligs Posterior portion Ischio-femoral ligament – Outer fibres spiral around femoral neck Deeper fibres arranged horizontally. Ligament and capsule allow minimal joint distraction
Netter F, Atlas of Human Anatomy, 2nd ed
Line of gravity (LOG)
Normal standing posture – LOG passes posteriorly to the hip joint. (Kendall; McCreary, & Provence, 1993,p 75) Produces a posterior tilt. In a closed chain, with the femur relatively fixed, posterior tilt → hip extension.
What controls gravity’s hip extensor moment ??? Hip flexor muscle activity ????
moon.ouhsc.edu/dthompso/NAMICS/hipbmk.htm
Phil Austin
LOG
moon.ouhsc.edu/dthompso/NAMICS/hipbmk.htm Phil Austin
Gravity’ s effect on the hip We don’t need activate muscles to stabilise the hip during neutral standing. Anterior ligaments exist in the same line of application (LOA)
moon.ouhsc.edu/dthompso/NAMICS/hipbmk.htm Phil Austin
Gravity’ s effect on the hip
The iliofemoral ligament elongates = very tight spring → elastic force.
This force is PASSIVE & not active (muscle force)
Directed to its point of attachments attachments on the ilium / femur
The force prevents the attachments being pulled further fu rther apart (PREVENTS EXTENSION) moon.ouhsc.edu/dthompso/NAMICS/hipbmk.htm
Phil Austin
Weight-Bearing
Trabeculae of bone line up along lines of stress. Along pubic rami, ischia and the dome of the acetabulae. (primary wt bearing areas) Primary wt bearing area is continuous with the MEDIAL TRABECULAR SYSTEM. (MTS) Trabeculae at the centre of the acetabulum – continuous with the LATERAL TRABECULAR SYSTEM. (LTS) Phil Austin
Medial Trabecular System Oriented along vertical compressive forces passing through the hip. Kapandji. I The Physiology of Joints, Vol 2, ed 5, Williams & Wilkins, Baltimore 1987.
Lateral Trabecular System Is oblique oblique – may develo develop p in response to shear stresses created by HAT pressing on the femoral head, while the GRF pushes up the femoral shaft. Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Kapandji. I The Physiology of Joints, Vol 2, ed 5, Williams & Wilkins, Baltimore 1987.
Trabecular Systems
Med / Lat systems also aid in resistance of bending stresses occurring at the femoral neck and shaft from weight from HAT.
Med system resists bending compression forces medially
Lat system resists bending tensile forces laterally.
Zone of weakness – Less reinforcement. Susceptible to bending forces, May #
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Phil Austin
Wt bearing causes bending forces along the shaft of the femur = Compression forces medially Tensile forces laterally
Wt bearing through the head of the femur & contraction of the abductors cause tensile forces superiorly & compressive forces inferiorly
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Primary Weight-bearing Areas
1) Dome of acetabulum Lies directly over the centre of rotation of femoral head. Greatest prevalence of degenerative change?? Phil Austin
2) Superior portion of femoral head Degenerative changes occur around / below the fovea or peripheral edge of articular surface. ∴ the primary weight bearing area
is not in the area of greatest degenerative change. Bombelli, R, et al: Mechanics of the normal and osteoarthritic hip: A new perspective, Clin Orthop, 182-6978,1984
Phil Austin
AP view of the left hip in a patient with osteoarthritis. The superior weight-bearing area of the joint space is quite narrowed.
Motion of Femur at Hip (Open Chain)
Typical ROM Flex – 90° (knee ext) Flex – 120 ° (knee flex) Ext – 10 – 30 ° Abd – 40 – 45 ° Add – 20 - 30 ° Lat / Med Rot – 42 - 50 ° (performed with hip at 90 ° flex)
Phil Austin
Osteokinematics
Phil Austin
Motion of femur at the hip (open Chain)
ROM is influenced if motion is a) passive OR active b) passive tension in a 2 joint muscle is encountered or avoided.
E.G. - Hip flexion is 90° with extended knee “ “ “ 120° with knee flexed
Release of passive tension on the 2 joint hamstring.
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Phil Austin
Motion of femur at the hip (open Chain)
Hip extension = 10 → 30° but is ↓ when knee flexion prompts passive flexion 2 joint rectus femoris.
Abduction = 45° ish – limited by gracilis Adduction = 25° ish – limited by TFL
Med / Lat rotation usually measured with 90 ° of flexion – 45 → 50°.
NB – Femoral anteversion → ↓ lat rotation, due to the femoral head is torsioned more anteriorly ∴Encounter of capsuloligamentous / muscular restrictions sooner. Phil Austin
Motion of Pelvis at Hip (Closed Chain)
Proximal segment moving on a fixed distal segment. Motion is the same as if the distal segment were the moving part.
Phil Austin
Anterior / Posterior Tilt
Motion of entire pelvis in a sagittal plane around a frontal axis Ant tilt – hip flex Post tilt – hip ext. Ant / post tilt results in flex / ext of hip joints together. Or at the closed chain joint if the opposite limb is open (none weight bearing) Phil Austin
www.pt.ntu.edu.tw/.. www.pt.ntu .edu.tw/.../KINspine/Pe ./KINspine/PelvicGirdle.htm lvicGirdle.htm Phil Austin
Lateral Tilt
A frontal plane motion of whole pelvis around a A/P axis. If ASIS’s are not horizontal – lateral tilt. Lateral tilt – 1 hip Jt is the pivot point (axis) for motion described on the other side. (hip hike or hip drop) ∴ None wt bearing hip is OPEN CHAIN Wt bearing hip is CLOSED CHAIN Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Phil Austin
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Phil Austin
The pelvis & wt have shifted Rt hip into adduction & left hip into abduction. Returning to neutral requires while putting weight through both feet the rt abductor & the left adductor work synergistically.
Levangie PK, Norkin CC. Joint Structure and Function, a Comprehensive Analysis. 3rd ed 2001
Pelvic Rotation
Entire pelvis moving in a transverse plane around a vertical axis through the middle of the pelvis in a bilateral stance Levangie, Norkin, Joint Structure and Function. 3 rd edit 2001.
Fwd rot of pelvis – side of pelvis opposite to supporting hip joint moves anteriorly. Stand on 1 leg and rotate pelvis – Feel relative rot.
Phil Austin
Lumbar-Pelvic Motion
OPEN CHAIN response due to the pelvis moving without necessitating motion elsewhere. NB – Subtle adjustments by other joints to assure that LOG remains within base of support. I.e. – planterflexion of ankles Phil Austin
Femur, pelvis and LS produce a ↑ ROM than in 1 segment alone.
Fwd bendin bending g to the floor floor – isol isolate ated d Flexion at the hip joints (anteriorly tilting pelvis on femurs) If the knees stay extended, hips only flex to 90° ∴Lumbar & thoracic flexion
incline the head & trunk fwd so Hands can reach the grounds EG of open chain response in hips & trunk (from above) NB – not an an eg of of how to pick pick up An object Phil Austin
Maximal abduction = 90°. If pure hip adduction = 45°
So must include lateral pelvic tilt & lateral flexion of the lumbar spine
Closed Chain Function
The 2 ends of the chain have to be fixed. Feet are fixed at 1 end. Head is functionally fixed at the other. NB - Although the head can move in space, it remains upright / vertically oriented. This is due to the influence of labyrinthin e and optical righting reflexes. reflexes.
∴ Drive to keep head upright over the sacrum – effectively fixes the head in relative space. ∴ Functionally fixed rather than structurally fixed. Phil Austin
Closed Chain Function
All the segments between the weight bearing part = 1 closed chain. ∴ Movement at 1 joint will create movement in at least 1 other linkage in the chain. ∴ Hip flexion cannot occur independently, but must be accompanied by motion at joints above and below.
Phil Austin
Open chain response to tight hip flexors a)
Inc ncli line ned d fo forw rwar ard d (LO (LOG G fa fall lls s ou outs tsid ide e base of of support support – No adjustm adjustment) ent)
Closed chain response to tight hip flexors b)
Spi pine ne ext xten ends ds to mai maint nta ain LOG wit ith hin base of support.
Muscle Function in Stance
BILATERAL STANCE
LOG – posterior to to axis for Flex / ext at hips
∴ ext moment of force → posterior tilt on pelvis and femoral heads.
Checked by passive tension in capsuloligamentous structures.
Ilio-psoas may assist passive structures.
Phil Austin
Flexors
Function primarily as mobility muscles in open chain. Secondarily – resistance to extension forces occurring as body passes over foot Ilio-psoas – primary hip flexion Rectus Femoris – only 1 of quad group that crosses hip and knee joint. (flex of hip, ext of knee)
Phil Austin
Flexors
Sartorius – flex, abd, and lat rot of the hip + (flex, med rot of the knee). Most important important when knee and hip are flexed (climbing stairs) Williams: Gray's Anatomy ed 38, Churchill Livingston 1995
Ilio-tibial band – flex, abd, med rot of femur on hip. Relieves tensile stresses imposed on femur by weight bearing forces TFL – Maintains tension in the ITB
Phil Austin
Hip Joint Musculature
Netter F, Atlas of Human Anatomy, 2nd ed
Adductors Function, not as prime movers But by reflex response to gait activities. Janda / Stara
Adductors may be synergists to Abductors when both feet are on ground - ↑ stability. 22.5% of muscle mass of lower extremity 18.4 18 .4 % - fl flex exors ors 14.9 14. 9 % - abd abduct uctors ors Ito. I.Morphological analysis of human Lower extremity based on the relative Muscle weight. Okajimas Folia Anat, 73 73 – 247-2 247-252 52 1996. 1996.
Extensors One joint gluteus maximus and two joint hamstring hams trings s – prima primary ry hip exten extensors sors Secondary assista Secondary assistance nce – post posterior erior fibres fibres of gluteus medius and superior fibres of adductor magnus and from piriformis. Hip extensi extension on via hamstri hamstrings ngs – redu reduced ced When the knee knee is flexed. Extension forces in the hip increase by 30% if the knee is extended.
Netter F, Atlas of Human Anatomy, 2nd ed
Abductors – Glut Abductors – Gluteus eus mediu medius s / minim minimus us + assistance from sartorius when abduction occurs against strong resistance. Glut med / min off set gravitational adduction Torque at stance hip (pelvis drop).
Lateral Rotators Apart from lat rot, these muscles act as ‘compresso ‘comp ressors’ rs’ and act as stabilizer stabilizers s (similar To rotator cuff at G/H joint. Lat rot action decreases with hip flexion. Medial Rotators No muscles that primarily act as med rot. Evidence suggest that the adductors are also Med rotators.
Netter F, Atlas of Human Anatomy, 2nd ed
Trend to increased med rot torque during hip Flexion (reduced lat rot
Muscle A flexes, internally rotates, and abducts the hip Muscle B extends, externally rotates, and abducts the hip Acting together, in a synergy, the two muscles can abduct the hip while producing little or no movement in other planes.
Phil Austin
Muscle Function in Stance Biomechanics
Phil Austin
Bilateral Stance
Erect bilateral stance – both hips are neutral or slight hyperextension & weight is evenly distributed through both legs. LOG – just posterior to axis of flex / ext. (frontal) = posterior tilt of pelvis on ” fixed fixed” femoral heads. Gravitational tension – checked by passive tension of capsularligamentous structures + slight / intermittent activity form iliopsoas. Levangie, Norkin, Joint Structure and Function. 3rd edit 2001.
Phil Austin
Bilateral Stance
In a frontal plane the superincumbent BW – transmitted through the SI´s, along the pelvic trabeculae system to Rt & Lt femoral heads. H.A.T. – (head, abdomen, thorax) ≅ ⅔ BW is distributed through both femoral heads. Gravitational torque occurs in the opposite direction BW on Rt hip drops the pelvis → Lt BW on Lt hip drops the pelvis → Rt
Phil Austin
These 2 opposing graviational moments of equal magnitude balance each other & the pelvis maintains equilibrium in a frontal plane.
Levangie, Norkin, Joint Structure and Function. 3rd edit 2001.
Bilateral Stance
If bilateral stance is not symetrical frontal plane muscles are required to control (adds & abds) Side to side motion Return to symetrical stance. In unilateral stance activity of adds in wt bearing or none wt bearing cannot contribute to stability of the stance limb. Sole domain of abductor function Phil Austin
Unilateral Stance
Full weight of HAT through load bearing hip E.g. – 90kg subject
HAT – ⅔ BW (60kg) 1 Lower limb – 1/6 BW (15kg).
∴ Supporting hip will endure 75kg (5/6 BW) of compression.
Rt hip joint compression = [2/3 x W] + [1/6 x W] = 5/6 x BW Levangie, Norkin, Joint Structure and Function. 3rd edit 2001.
Phil Austin
Hip abds – momen momentt arm of 50mm 50mm The pull of the abds (Fms) on a horizontal pelvis will resolve the translatory component (Ft) 50mm
100mm
This pulls the acetabulum to the centre of the femoral head. The rotatory component (Fr) pulls the pelvis down on the superior aspect of the femoral head
Unilateral Stance
Force of gravity on HAT and none WB lower limb (HATLL) – add force to the supporting hip. LOG ≅ 100mm (0.1m) from right hip axis [MA = 100mm] Actual MA – slightly ↑ due to wt of hanging Lt leg will pull COG slightly → Lt Simple Hypothetical e.g. HATLL Torque adduction 75kg x 0.1m = 7.5 N -m Phil Austin
Unilateral Stance
Maintenance of single limb support → countertorque abduction of equivilent force. This is produced at glut medius / minimus These muscles must generate an equivilent equivil ent abduction torque of 7.5 N m Torque abduction
= 7.5 N m / 50mm (0.05m) = Fms
Fms = 7.5 N m = 150kg 0.05m Phil Austin
Unilateral Stance
∴ prevention of the pelvis falling → unsupported side
The abds must generate a force of at least 150 kg.
Assuming all the muscular force is transmitted through the femoral head, the 150kg must now be b e added to the 75 kg of compression due to BW. f orce at the ∴ total hip compression or joint reaction force stance hip
= 150 kg + 75 kg ≥ 225 kg total hip joint compression Phil Austin
Unilateral Stance
Hypothetical figures simplify forces involved. Total joint compression / reaction forces = 2.5 -3 x BW in a unilateral stance. Investigations also calculate 4 – 7 x BW respectively at begining & end of ” stance stance phase” of gait & 7x when climbing the stairs Phil Austin
Unilateral Stance
Wt loss may help reduce joint reaction.
Magnitudes of force differ in different individuals i.e. ∠ of pull & and the ∠ of inclination of the femoral head.
Physiological / biomechanical factors causing ↑ force production at hip abds – in time may accelerate joint deterioration.
Phil Austin
Compensatory Lateral Lean
Gravitational force can be ↓ by laterally leaning the trunk over the pelvis toward the side of pain / weakness when in a unilateral stance. May appear to be counterproduc counterproductive tive (apparent ↑ BW) BUT – swings LOG closer to the hip joint ∴ ↓ graviational MA.
Phil Austin
Compensatory Lateral Lean
HATLL must pass through regardless ∴ leaning toward doesn’ t increase joint compression. ∴ The shorter the gravitational adduction torque = ↓
need for abduction counter torque
EG – If lateral lean is bought to 25mm of the right hip the gravitational torque would be.
Phil Austin
HATLL torque
adduction
=
5/6 BW (75kg) x .025m HATLL torque
0.05m
adduction
= 1.875 N m
If only 1.875 N m were produced by BW on the Rt hip hip – the abds abds force force needed needed would be. Torque
abduction
= 1.875 N m / 0.05m = Fms
0.025m
Fmss = 1. Fm 1.87 875 5 N m = 37 37.5 .5kg kg .05m 37.5 kg of muscular joint compression + 75 kg of BW compression Total hip joint compression ≥ 112.5kg
Phil Austin
Sacral Articulating Surface
Auricular (c) shaped, Foetal – prepuberty – surfaces are flat and smooth Postpubertal – surface is marked by a central groove or surface depression that extends the length of the articulating surface
Sacral cartilage cartilage is 1.5 : 1 to 3 : 1 thicker than than iliac cartila cartilage.
↑ thickness in females : males.
Bowen,Cassidy. Macroscopic and microscopic anatomy of sacroilia c from embryonic life until 8 th decade. Spine, 6 620--627. 1981 620
Phil Austin
Articulating Surface of the Ilia
Also C-shaped
Smooth / flat to prepuberty
Postpuberty – central ridge along length. Corresponds with groove at sacral surface. Both surfaces lined with type II collagen (hyaline)
Phil Austin
Iliac Articulations
In Childhood – permits glide in all ranges r anges (synovial (synovial joint). Postpuberty – joint surfaces change configuration and translation and rotation is restricted to a few mm’s (open to controversy)
Walker.JM. The sacroiliac joint, A critical review. Phys Ther 72, 903, 1992.
Nutation – Anterior motion of sacral promontory.
↓ A/P dia at pelvic brim
↑ A/P dia at pelvic outlet.
Important during pregnancy especially under influence of RELAXIN . Ligamentous structures are softened.
Phil Austin
Symphysis Pubis Articulation
Cartilaginous joint. Each end of the pubis bone – covered with articular cartilage. Joint formed by fibrocartilaginous disc – joins hyaline covered ends. The disc has a thin central cleft (in females may extend along the length. Kapandji IA. Physiology of joints 3, ed 22 Churchill Churchill Livingstone, Livingstone, Edinburgh, 1974
Phil Austin
Symphysis Pubis Articulation
3 Ligaments associated with pubis joint
Superior pubic lig – thick / dense fibrous band attaching to pubic crest and tubercles – support of superior aspect of joint.
Inferior pubic lig – Arches from ramus to ramus . Posterior pubic lig – Continuous with the periosteum of the pubic bones.
Anterior Pubis – re-enforced by aponeuroses from muscles crossing the joint.
Phil Austin
Function of Sacral Region
HAT creates a nutation torque on the sacrum. Ground Force (GF) creates posterior torsion on the ilia. Nutation / counternutation & posterior torsion of the ilia are prevented by ligamentous tension and adjacent muscles. Phil Austin
Function
SI’s and pubis – linked by closed kinematic chain ∴ any motion occurring at the pubis WILL be accompanied by motion at the SI’s and vice versa.
SI’s / pubis – functionally related to hips. ∴ effect and affected by motion from trunk and ↓ extremity. ∴ Shifting weight from 1 leg to another WILL induce motion at the SI’s.
Fusion of lower lumbars have been found to increase motion at the SI’s Grieve, GP, The sacro-iliac joint. Physiotherapy 62.8. 1979
Phil Austin
Function
Shearing forces created at the pubis during single leg support phase of walking due to lateral pelvic tilting. If pubis is dislocated = instability. ∴ ↑ stress on SI’s, hips and vertebral column.
Phil Austin
Pelvic Floor Muscles
Voluntary contraction of levator ani helps constrict openings of urethra and anus. Involuntary contraction occur during coughing or holding breath etc ↑ intra-abdominal pressure. In women, these muscles surround the vagina and help support the uterus. The coccygeus muscle assists the levator ani in supporting pelvi c viscera + maintain intra- abdominal pressure.
Phil Austin