exam 2 lecture 7/8 Flashcards
GTPS:
- primary cause of:
- weak ___ _____
- plays a role:
- lateral hip pain
- hip abductors
- tension stress; also compression (midstance & TFL)
what is Trendelenburg sign?
weak hip falls into pelvic on femoral adduction
contralateral hip drop
what is an uncompensated response of trendelenburg sign?
weak hip abductors
opposite side hip drop
what is a compensated response of Trendelenburg sign?
weak hip abductors
line of gravity shifts towards weak hip
when does the piriformis act as an external rotator?
hip extended, anatomical position
line of pull is posterior to the vertical axis of rotation
when does the piriformis act as an internal rotator?
hip flexed
using a cane reduces: (2)
compressive forces if in opposite hand
JRF by reducing activation of hip abductors (36%)
counterclockwise forces (hip ____) = clockwise forces (_____ and ______ weight held)
abd
BW; contralateral
connective tissue reinforcement of posterior capsule:
oblique popliteal ligament
arcuate popliteal ligament
muscular reinforcement of posterior capsule:
popliteus
gastroc
hamstrings
connective tissue reinforcement of posterior lateral capsule:
arcuate popliteal ligament
LCL
popliteofibular ligament
muscle reinforcement of posterior lateral capsule:
tendon of popliteus
where does the medial capsule run?
patellar tendon to posterior capsule medial side
connective tissue reinforcement of medial capsule:
- anterior 1/3:
- middle 1/3:
- posterior 1/3:
- thin layer of fascia - medial patellar retinacular fibers
- medial pat retinacular fibers, superficial and deep MCL
- thick! starts near adductor tubercle, blends w SM tendinous expansion and posterior capsule & posterior oblique ligament. Pes anserine reinforces
muscular reinforcement of medial capsule:
SM
SGT - pes anserine
TF joint:
- _____, ______ femoral condyles. _____, ______ tibial plateaus
- ______ motion but ______ _____ provides stability
- ______ acts as gaskets to form seats for the femoral condyles
- large, convex. flat, smaller
- excessive; soft tissue
- menisci
menisci:
- anchored to intercondylar region of tibia @ ____
- external edge of each meniscus is attached to tibia and the capsule by _____ _______
- the two are connected anteriorly by _______ ______
anterior/posterior horns
coronary ligaments
transverse ligament
what muscles are attached to the menisci which helps to stabilize
quads
SM
popliteus to lateral
which ligament in the knee attaches to the meniscus? which does NOT?
MCL
LCL (only attaches to lateral capsule)
what is the blood supply of the meniscus?
outer 1/3 - direct from genicular arteries (“red zone”)
inner 2/3 - avascular (“white zone”)
nutrition from synovial fluid (needs movement!)
what is the primary function of the menisci?
decrease compressive forces (triples joint contact area, decreases pressure on articular cartilage)
becomes tensile stress and spreads out like a hoop
what are secondary functions of meniscus?
stabilizing joint during motion
lubricating articular cartilage
providing proprioception
help guide arthokinematics
how do meniscal tears most often happen?
forceful, axial rotation of the femoral condyles over a flexed WB knee
risk increases with ligamentous laxity and malalignment
what side of the meniscus is injured twice as frequently?
medial
valgus force (large stress on MCL/post-med capsule)
ROM for knee flex & ext:
130-150 flex
5-10 hyperext
what does the IAR or evolute in the knee do?
lengthens the moment arm of flexors and extensors musculature
ROM of knee for IR/ER at 90 deg
40-45 deg
ER > IR
how is rotation of the knee named?
position of tibial tuberosity relative to the anterior distal femur
*** slide 26
tibial-on-femoral extension:
Meniscus pulled:
tibia rolls and slides anteriorly on femur
meniscus pulled anteriorly by quads
femoral-on-tibial extension:
___ directs the roll
femoral condyles roll anteriorly and slide posteriorly on tibia
quads direct the roll and stabilizes the meniscus vs posterior shear of femur
what is the screw home mechanism?
full ext requires 10 deg ER during last 30 deg of ext. this increases joint stability.
in open chain ext, tibia ER
in closed chain ext, femur IR
what is the screw home mechanism driven by?
shape of femoral condyle (tibial follows medial condyle and creates ER) medial is longer
passive tension in ACL
slight lateral pull of quads
explain the screw home mechanism for flexion?
opposite!
unlocking IR happens first - driven by the popliteus (can rotate femur or tibia)
MCL:
- ____ and _____
- resists what force?
—superficial:
—deep:
- flat and broad
- valgus force (abd)
— esp w knee flexed 20-30 deg
— esp w knee in full ext (resist knee ext)
LCL:
- ____, cord like
- resists what force?
- short
- varus force (add), knee ext, rotation extremes
primary function of MCL and LCL
limit motion in frontal plane
what are common mechanisms of injury of MCL?
valgus producing force with foot planted (‘clip’ in football)
severe hyperext of knee
what are common mechanisms of injury of LCL?
varus producing force with foot planted
severe hyperext of knee
function of ACL and PCL
resist extremes of all motions - primarily A-P shear forces between tibia and femur in sagittal plane motions (cutting)
helps guide arthrokinematics and provides proprioceptive feedback
ACL:
- runs?
- 2 bundles:
— AntMed bundle taut in:
— PostLat bundle taut in:
- mostly resists?
- posterior, superior, and lateral to medial side of lateral condyle
— knee flexion
— knee ext - extension
general mechanics of ACL
last 50-60 deg ext:
force of quads pulls tibia ant and thus tension in ACL limits the slide
common mechanisms of injury of ACL
large valgus producing force with foot planted
large axial rotation applied to knee with foot planted
sever hyperext of knee
landing, decelerating, cutting, pivoting over single limb
strong quad activation: excessive ER
PCL:
- ____ than ACL
- increasingly taut with greater _____
- ____ glide partially limited by PCL
- injuries common or rare?
- thicker
- flexion (90-120 >est)
- posterior
- rare
PCL MOI:
high energy trauma
falling onto a fully flexed knee (dashboard injury)
PF at 135 deg flex:
superior pole below groove at lateral and odd facets
PF at 90-60 deg:
in trochlear groove
contact area the greatest (only 1/3 area)
PF at 20-30 deg:
contact at inferior pole
lost much of its mechanical engagement with groove
PF at full ext:
rests completely proximal to groove on suprapatellar fat pad
