Knee kinematics Flashcards
what structures are included in the anterior portion of the knee capsule
patella and tendon
what muscles reinforce the anterior portion of the knee capsule
quads
what connective tissues reinforce the anterior portion of the knee capsule
extensions of the ITB, vastus lateralis and medius
what connective tissues reinforce the lateral portion of the capsule
LCL
lat patellar retinacular fibers
ITB
what muscles reinforce the lateral portion of the capsule
biceps femoris
tendon popliteus
lat head of gastroc
what connective tissue reinforces to posterior portion of the knee capsule
oblique popliteal lig
arcuate popliteal lig
what muscles reinforce the posterior portion of the knee capsule
popliteus
fastrocs
hamstrings
what connective tissue supports the posterior lateral knee capsule
arcuate popliteal ig
LCL
popliteofibular lig
what muscles support the posterior lateral capsule of the knee
tendon of popliteus
what sesamoid bone in the posterolateral capsule of the knee varies widely in humans
fabella
the anterior 1/3 of the medial capsule is reinforced by what structures
thin layer of fascia
medial patellar retinacular fibers
the middle 1/3 of the medial knee capsule is reinforced by which structures
medial pat retinacular fibers
superficial and deep MCL
the posterior 1/3 of the medial knee capsule is reinforced by which structures
starting neard adductor tubercle blendin with SM tendinosis expansion and posterior capsule and posterior oblique ligament
reinforced by pes anserine
what muscles reinforce the medial portion of the knee capsule
SM
SGT
pes anserine
describe the synovial joint of the knee
internal capsule lined with synovial membrane
14 bursa at inter-tissue junctions
suprapatellar and deep infrapatellar fat pads
describe the tibiofemoral joint
large convex femoral condyles and flat, smaller tibial plateuas
what is the function of the menisci in the tibiofemoral joints
menisci act as gaskets to form seats for the femoral condyles
where are the menisci anchored to the intercondylar region of the tibia
anterior/posterior horns
the external edge of each meniscus is attached to tibia and the capsule by ___ ligs
what are the ligs functions
coronary
ligs are loose and allow pivoting
what structure connects the anterior/posterior horns and the coronary ligaments anteriorly
transverse ligaments
what are the secondary mm that attach to the menisci
quads
semimembranosus
popliteus to lateral
what does the medial menisci attach to
MCL and adjacent capsule
what does the lateral menisci attach to
lateral capsule
what structure passes between the LCL and lateral meniscus
popliteus
what is the “red zone” of the menisci
the outer 1/3 of the menisci
the area of the menisci that receives blood supply
what arteries supply the menisci
genicular arteries (branches off the popliteal artery)
what is the “white zone” of the menisci
inner 2/3 of the menisci
area that is avascular
what is responsible for supplying nutrition to the menisci
synovial fluid
how do the menisci change during weight-bearing activities
meniscus deforms peripherally and creates tensile stress
list the order of increasing stress with walking, stepping, up stairs, or cycling on the menisci
cycling < walking < going up stairs
compete lateral meniscectomy increases peak contact pressure ___%
230%
__% of load goes through the lateral mensici and __% goes through meniscus
70% in lateral
50% in medial
what are the secondary functional considerations of the tibiofemoral joint
stabilizing join during motion
lubricating articular cartilage
providing proprioception
help guide arthrokinematics
list some of the most common mechanisms of injury of the tibiofemoral joint
forceful, axial roation of the femoral condyles over a flexed WB knee
dislodged/folded flap can mechanically block knee motion
medial injured twice as frequently - valgus force
risk increases with ligamentous laxity and malalignment
what is the normal range of flexion of knee flexion
130-150 degrees
what is the normal range of hyperextension of the knee
5-10
how does the IAR or “evolute” have biomechanical implications
lengthens the moment arm of flexors and extensors musculature
brace might piston - need align to the “average” axis of the lateral epicondyle
describe the axis of axial rotation of the knee
longitudinal axis through tibia
at 90 degrees of knee flexion, what is the normal range of axial rotation
40-45 degrees
ER : exceeds IR
2:1
how is the rotation of the tibiofemoral joint named
named by the position of tibial tuberosity relative to the anterior distal femur
describe the arthrokinematics of tibia-on-femoral extension
tibia rolls and slides anteriorly on fenur
meniscus pulled anteriorly by quads
describe the arthrokineamtics of femoral-on-tibia extension
femoral condyles roll anteriorly and slide posteriorly on tibia
quads direct the roll and stabilize the meniscus vs posterior shear of the femur
describe “screw home”
full extension requires 10 degrees ER during last 30 degrees of extension
increases joint congruence/stability
open chain ER, CC femur IR
what is “screw home” driven by
shape of the femoral condyle
passive tension in ACL
slight lateral pull of quads
what motion causes the unlocking IR first
what muscle controls this
flexion unlocks IR first
driven by popliteus
describe the arthrokinematics of IR/ER
knee must be flexed
spin between menisci and articular surfaces of tibia and femur
axial rotation of femur over tibia causes menisci to deform/compress
popliteus and semimembranosus help stabilize
describe the superficial part of the MCL
well-defined parallel fibers
medial epicondyle to medial patella to medial proximal tibia
describe the deep part of the MCL
slightly posterior and distal
shorter and oblique
attaches to capsule, medial meniscus, semimembranosus tendon
describe the LCL
short and chord like
runs vertically from lateral epicondyle to fibular head
does not attach to adjacent meniscus
blends with biceps femoris tendon
what structure runs between the lateral meniscus and the LCL
tendon of popliteus
what is the primary function of the MCL and LCL
limit motion in frontal plane
MCL resists __ force when the knee is extended
valgus
LCL resists ___ force when the knee is extended
varus
what is the secondary function of the LCL and MCL
provide general stabilizing tension
protecting against rotation extremes
describe the blood supply to the ACL and PCL and how it affects the healing process
limited blood supply
slows healing process
what is the function of the ACL and PCL
resist extremes of all motions
primarily resists AP shear forces between tibia and femur
t/f
the ACL and PCL help to guide arthrokinematics and provides proprioceptive feedback via mechanoreceptors
true
when is the ACL most taut
some fibers taut in flx but increasingly taut as reach ext
how does the ACL run
runs posterior
superior and lateral to medial side of lateral epicondyle
what muscle is responsible for pulling tibia anterior during ext
what is the effect on the ACL
quads pull tibia ant last 50-60 degrees ext
tension on ACL limits slide
what is the anterior drawer test
why is this test used to test the ACL
leg is at 90 degrees
PT pulls proximal tibai anterior
ACL is 85% of passive resistance to anterior glide
what muscle, if contracted incorrectly, affects the results of the anterior drawer test
why/how
hamstring spasm will prevent tibia from anterior glide if the ACL is damaged
d/t the attachment of the hamstrings on the tibial and fibula head
__% of sports-related to ACL are noncontact
70%
what are some mechanisms of injury to the ACL
strong quad activation
valgus collapse
excessive ER
hyperextension
when is the PCL most taught
knee flexion
explain the posterior drawer test
proximal end of tibia posterior
knees in 90 degrees
knees sag at 90 degrees hip/knee flexion
what are the common mechanisms on injury to the PCL
high energy trauma
falling onto a fully flexed knee - “dashboard injury”
what muscle is the stabilizer of the patellofemoral joint
quad
tibial on femoral patella slides relative to
fixed trochlear groove
femoral on tibial (squat) the trochlear groove slides relative to
fixed patellla
