MSK TBL 13: Pelvis, Hip, & Gluteal Region Functional Anatomy

hip bone [os coxae] made up of

ilium, ischium, & pubis

• at birth, bones joined by hyaline cartilage

• at puberty, separated by Y-shaped triradiate cartilage

• fusion begins 15-17 yrs, completes 20-25 yrs

ilium

• largest bone of hip

• contributes part of upper acetabulum

• features

  • ala [“wing”]

  • iliac crest

  • ASIS & AIIS

  • iliac fossa

    • *osteoporosis may thin iliac fossa

    • where iliacus sits

  • auricular surface

    • articulates w/ sacrum at sacroiliac joint

  • gluteal lines

    • muscle attachment for glute muscles

ischium

• forms posteroinferior part of hip bone

• main parts

  • body

  • ramus

  • ischial spine

    • separates greater & lesser sciatic notches

  • ischial tuberosity

    • supports body weight when sitting

    • origin of posterior thigh muscles

iliac tubercle

• 5-6 cm behind ASIS

• marks widest iliac crest point, aligned w/ L5 vertebra

posterior sacro-iliac ligament

continues into the sacrotuberous ligament

sacrotuberous & sacrospinous ligament

convert sciatic notches into greater & lesser sciatic foramen

sacrotuberous ligament

runs from posterior iliac spines, sacrum, & coccyx → medial ischial tuberosity

sacrospinous ligament

• lies deep to sacrotuberous ligament

• runs from lower sacrum & coccyx → ischial spine

• lies edge-to-edge w/ levator ani muscle, forming pelvic floor

key contents of greater sciatic foramen [below piriformis]

POP SI

• Pudendal nerve

• Obturator internus nerve

• Posterior cutaneous nerve of thigh

• Sciatic nerve

• Inferior gluteal nerve

key contents of greater sciatic foramen [above piriformis]

superior gluteal nerve [& artery & vein]

key contents of lesser sciatic foramen

PIN + Tendon

• Pudendal nerve

• Internal Pudendal Vessels

• Nerve to obturator internus

• Obturator internus Tendon

• immediately hook forward around ischial spine/ligament to enter perineum via lesser sciatic foramen

*PIN gives spatial relationship from medial → lateral

iliofemoral ligament

• reinforces anterior joint capsule

• motion restricted

  • anterior fibers: hyperextension

  • superior fibers: adduction

  • inferior fibers: abduction

• allows standing w/ minimal muscular effort

pubofemoral ligament

restricts abduction & hyperextension

ischiofemoral ligament

restricts internal/medial rotation & extension

zona orbicularis

restricts femoral head distraction

gluteus maximus

• origin

  • posterior ilium [behind posterior gluteal line], sacrum, coccyx, sacrotuberous ligament

• insertion

  • iliotibial tract [superior fibers]

  • gluteal tuberosity [deep fibers]

• innervation

  • inferior gluteal nerve [L5, S1, S2]

• action

  • extends hip

  • lateral rotator

  • trunk extension when femur fixed

  • acts w/ TFL via IT tract to stabilize pelvis

trochanteric bursa

• btwn superior fibers of gluteus maximus & greater trochanter

• most prominent at birth

• lateral hip pain w/ bursitis

ischial bursa

• btwn inferior glute max & ischial tuberosity

• can become inflamed in prolonged sitting [“weaver’s bottom”]

gluteofemoral bursa

• btwn iliotibial tract & vastus lateralis

• decreased friction during lateral thigh movement

gluteus medius

deep to glute max, superior to minimus

• origin

  • external ilium [btwn anterior & posterior gluteal lines]

• insertion

  • lateral surface of greater trochanter

• innervation

  • superior gluteal nerve [L5, S1]

• action

  • abducts & medially rotates thigh

  • stabilizes pelvis in gait

• clinical

  • weakness → Trendenlenburg gait

  • target for deep intramuscular injections [upper outer quadrant]

gluteus minimus

• origin

  • lower ilium

  • margin of greater sciatic notch

• insertion

  • greater trochanter of femur

• innervation

  • superior gluteal nerve [L5, S1]

• action

  • anterior fibers assist w/ hip flexion where primary hip flexors [Iliopsoas, Rectus femoris]

stance phase [weight bearing limb]

abductors stabilize pelvis & rotate femur medially

aid limb propulsion

swing phase [non-WB limb]

lateral rotators [piriformis, obturator internus]

tensor fascia latae [TFL]

anterior part of lateral thigh; superficial layer

• origin

  • ASIS & anterior iliac crest

• insertion

  • iliotibial tract → lateral condyle of tibia

• innervation

  • superior gluteal nerve

• action

  • flexes, abducts, & medially rotates thigh

  • stabilizes knee via IT tract

• clinical

  • overactive in tight IT band syndrome or runners

Piriformis

deep gluteal muscle; passes thru greater sciatic foramen

• origin

  • middle 3 sacral segments S2-S4

• insertion

  • superior border of greater trochanter

• innervation

  • anterior rami [S1, S2]

• action

  • lateral rotation of extended thigh

  • abduction when thigh is flexed

• clinical

  • piriformis syndrome

obturator internus [OI]

exits lesser sciatic foramen

• origin

  • pelvis surface of obturator membrane & surrounding bones

• insertion

  • medial surface of greater trochanter [trochanter fossa]

• innervation

  • nerve to obturator internus [L5, S1]

• action

  • laterally rotates extended thigh

  • abducts flexed thigh

• levator ani & OI forms part of lateral wall of both pelvis & perineum

• clinical

  • one of key muscles in triceps coxae

superior gemellus

• origin

  • ischial spine

• insertion

  • medial surface of greater trochanter [trochanteric fossa]

• innervation

  • nerve to obturator internus

• action

  • work w/ OI to laterally rotate & abduct hip

  • stabilize joint

• clinical

  • often fused & act in concert

  • part of triceps coxae

inferior gemellus

• origin

  • ischial tuberosity

• insertion

  • medial surface of greater trochanter [trochanteric fossa]

• innervation

  • nerve to quadratus femoris

• action

  • work w/ OI to laterally rotate & abduct hip

  • stabilize joint

• clinical

  • often fused & act in concert

  • part of triceps coxae

quadratus femoris

short, flat, rectangular muscle

inferior to obturator internus & gemelli muscles

• origin

  • lateral border of ischial tuberosity

• insertion

  • quadrate tubercle on intertrochanteric crest of femur

• innervation

  • nerve to quadratus femoris [L5, S1]

• action

  • lateral rotation of thigh

  • stabilize femoral head

• clinical

  • works w/ adj. rotators to maintain joint congruency

obturator externus [OE]

lies deep in proximal thigh, posterior to pectineus & adductors

• origin

  • external surface of obturator membrane & surrounding bone

• insertion

  • trochanteric fossa of femur

• innervation

  • obturator nerve [L3, L4]

    • unique b/c others mostly innervated by sacral plexus

• action

  • lateral rotation of thigh

    • most effective when hip is flexed

semitendinosus [ST]

long tendinous lower half

lies superficial to semimembranosus

• origin

  • ischial tuberosity

• insertion

  • medial surface of superior tibia [part of pes anserinus]

• innervation

  • tibial division of sciatic nerve [L5, S1, S2]

• action

  • hip extension, knee flexion, medial rotation of leg when flexed

  • aids in trunk extension when legs are fixed

semimembranosus [SM]

flat, broad, membranous muscle

lies deep to ST

• origin

  • ischial tuberosity

• insertion

  • posterior medial condyle of tibia

• innervation

  • tibial division of sciatic nerve

• action

  • extends hip, flexes knee, medially rotates flexed leg

  • helps stabilize knee joint

biceps femoris [long head]

lateral muscle of posterior thigh

unites w/ short head lower down

• origin

  • ischial tuberosity

• insertion

  • head of fibula [via common tendon w/ short head]

• innervation

  • tibial division of sciatic nerve [L5-S2]

• action

  • extends hip, flexes knee, laterally rotates flexed leg

superior clunial nerves

• L1-L3 [posterior rami]

• skin over iliac crest & upper gluteal region

middle clunial nerves

• S1-S2 [posterior rami]

• skin over sacrum & adj. buttocks

inferior clunial nerves

• branches of posterior cutaneous nerve of thigh [S2-S3]

• skin of lower buttocks toward greater trochanter

Spinal levels of sacral plexus

SIPPS

• Sup Glut N to quad fem/inf gem

  • L4, L5, S1

    • sometimes only considered L5, S1

• Inf Glut N to Obt Int/Sup Gem

  • L5, S1, S2

• Post Cut N of thigh

  • L1, L2, L3

• Pudendal

  • S2, S3, S4

• Sciatic

  • L4, L5, S1, S2, S3

sciatic nerve

• largest nerve in body

• formed at inferior border of piriformis

• passes midway btwn greater trochanter & ischial tuberosity

• splits into

  • tibial nerve: anterior division

  • common fibular nerve: posterior division

• clinical

  • piriformis syndrome when common fibular nerve pierces or runs over piriformis [anatomy in 12% of people]

nerve to quadratis femoris exits pelvis…

anterior to sciatic nerve

nerve to obturator internus courses…

posterior to sacrospinous ligament & reenters via lesser sciatic foramen

arterial supply of gluteal region: major branches

• superior gluteal artery

• inferior gluteal artery

• internal pudendal artery

superior gluteal artery

• largest branch of interal iliac

• superficial branch

  • glute max & overlying skin

• deep branch

  • glut med, min, & TFL

• anastomoses w/ inferior gluteal & medial circumflex femoral arteries

artery to sciatic nerve

• gives off slender companion artery of sciatic nerve [arteria comitans nervi ischiadici]

• anastomoses w/ superior gluteal, perforating, & circumflex femoral arteries

internal pudendal artery

• arises from internal iliac

• follows pudendal nerve [greater → lesser sciatic foramen]

• supplies perineum

• does NOT supply gluteal region or posterior thigh

perforating arteries [from profunda femoris]

• pierce adductor magnus → posterior thigh

• supply hamstrings & sciatic nerve

fracture of femoral head

• medial circumflex femoral & retinacular arteries are torn

• femoral head may undergo avascular necrosis [AVN]

Bonnet’s position

flexion, abduction, external rotation

• pts w/ intra-articular hip issues [labral tears, femoroacetabular impingement, early osteoarthritis, or capsular tightness] find relied in this position

Neck-shaft angle [frontal plane angle]

• normal: 120-135 degrees

• Coxa valga: >140 degrees

  • → genu varum

• Coxa vara: <120 degrees

  • → genu valgum

  • alters glute med stability → hip instability

Femoral Version [Transverse plane or Angle of Femoral Torsion]

angle btwn femoral neck & condyles

• Normal: 10-20 degrees

• Anteversion: >20 degrees

  • toe-in gait

• Retroversion: <10 degrees

  • toe-out gait

3 main causes of in-toeing [“pigeon toed”] gait

1. thigh: increased femoral anteversion

   1. in-toe gait & patella turned inward

2. leg/shin: internal tibial torsion

   1. in-toe gait but patella facing straight

3. foot: metatarsus adductus

   1. medial deviation of metatarsals

      1. curved, C-shaped lateral foot margin

FAIR test

Flexion, Adduction, Internal Rotation

• tests piriformis

FABER test

Flexion, ABduction, External Rotation

• tests hip flexors [iliopsoas], adductors, sartorius

Ober’s test

tests TFL