Functional anatomy of the pelvis

Question 1

SI joints have?

Answer 1

• atypical joint surfaces

- diarthosis (true synovial joint)

Question 2

SI morphology of L shape (boot)

Answer 2

• Upper half (leg) articulates at level of S1

- Lower half (foot) articulates level of S2-3

Question 3

SI morphology sacral surface seg. (1-3)

Answer 3

• hyaline cartilage (blue, 3x thicker than iliac surface)
• central groove (concavity)
• wedge shape S to I
• Has S-shape A to P

Question 4

SI morphology w/ iliac surface (PSIS to PIIS)

Answer 4

• fibrocartilage (yellow)
• central convex ridge
• lg. Rough boney surface PS to joint for ll attachment (iliac tuberosity)

Question 5

SI morphological changes at birth

Answer 5

• joints undeveloped: smooth, flat (move any direction) and ll provide stability
• development starts with walking

Question 6

SI morphological change during teens

Answer 6

• roughening of surfaces: grooves/ridges (male more pronounced)
• track bound motion starts

Question 7

SI morphological change in the 3rd - 4th decades

Answer 7

• articular change in surfaces well developed
• joint surfaces become more irregular
• enlargement of iliac tub and depression
• start of joint erosion
• maybe osteoarthritic (DJD) on iliac surface (more one males)

Question 8

SI morphological changes in the 5th-6th decade

Answer 8

• joint surface more irregular
• topograhy unique to each joint (more in males)
• maybe osteoarthrosis (DJD) sacral w/ cont. on iliac tub ( more in men)
• maybe joint adhesions, osteophytes, fusion

Question 9

SI morphological changes in the 7th decade

Answer 9

• interarticular adhesions
• fusion(high prevalance of boney ankylosis: m/27.7% f/2.3% and age for men: 20-30y 5.8%, 60-70y 31.1%, 80+y 46.7%)
• fusion mainly in Spart of the joint

Question 10

What are intrensic SI ll?

Answer 10

Bind sacrum to the ilium so as to limit movement and provide support

Question 11

P intrensic SI ll

Answer 11

• interossious (massive +major stablizer)

- dorsal ll

Question 12

What do do P dorsal SI ll do?

Answer 12

• smaller, do less for stablization
• sacrum to PISI to iliac tub.
• limits Nutation
• dorsal rami go b/w interossious and SI ll

Question 13

A intrensic SI ll

Answer 13

Thin seen as a thickenin g of the A joint capsule

Question 14

Intrensic joint capsule

Answer 14

Good A development and poor P development

Question 15

What do extrensic ll do?

Answer 15

-sacrotuberous ll and sacrospinous ll limit P motion of sacral apex (counternutation)

Question 16

What are the attacmet points of the sacrotuberous ll?

Answer 16

I portion of sacrum to the ischial tuberosity

-limits counternutation

Question 17

What are the attacmnet points of the sacrospinous ll?

Answer 17

I lateral edge of the sacrum and upper edge of the coccyx to the ischial spine
-limits counternutation

Question 18

Symphysis pubis

Answer 18

• amphiarthrosis

- intrapubic fibrocartilagenous disc

Question 19

Mm acting on SI joint

Answer 19

• NO mm directly cross SI

- NO mm act on SI directly, many mechanically influence SI and respond to stress applied

Question 20

Mm that can load SI

Answer 20

• erector spinae
• quadratus lumborum
• psoas
• iliacus
• piriformis
• gluteals

Question 21

Mm relating to SI dysfunction

Answer 21

• mm react to SI stress (can caouse spasms, trigger points)

- abnormal mm tension cN limit SI motion causing joint dysfuncrion

Question 22

Innv of the SI

Answer 22

• direcr innv is debated

- neral elements in capsule, adjoining ll (suggests innv for pain and propriception)

Question 23

What does a true synovial joint have?

Answer 23

• Joint capsule
• synovial fluid
• joint cavity