exam 2 lecture 7/8 Flashcards by Demond Fleming

GTPS:
- primary cause of:
- weak ___ _____
- plays a role:

lateral hip pain
hip abductors
tension stress; also compression (midstance & TFL)

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what is Trendelenburg sign?

weak hip falls into pelvic on femoral adduction
contralateral hip drop

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what is an uncompensated response of trendelenburg sign?

weak hip abductors
opposite side hip drop

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what is a compensated response of Trendelenburg sign?

weak hip abductors
line of gravity shifts towards weak hip

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when does the piriformis act as an external rotator?

hip extended, anatomical position
line of pull is posterior to the vertical axis of rotation

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when does the piriformis act as an internal rotator?

hip flexed

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using a cane reduces: (2)

compressive forces if in opposite hand
JRF by reducing activation of hip abductors (36%)

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counterclockwise forces (hip ____) = clockwise forces (_____ and ______ weight held)

abd
BW; contralateral

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connective tissue reinforcement of posterior capsule:

oblique popliteal ligament
arcuate popliteal ligament

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muscular reinforcement of posterior capsule:

popliteus
gastroc
hamstrings

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connective tissue reinforcement of posterior lateral capsule:

arcuate popliteal ligament
LCL
popliteofibular ligament

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muscle reinforcement of posterior lateral capsule:

tendon of popliteus

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where does the medial capsule run?

patellar tendon to posterior capsule medial side

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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

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muscular reinforcement of medial capsule:

SM
SGT - pes anserine

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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

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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

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what muscles are attached to the menisci which helps to stabilize

quads
SM
popliteus to lateral

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which ligament in the knee attaches to the meniscus? which does NOT?

MCL
LCL (only attaches to lateral capsule)

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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