Lecture 9: Knee Musculature Flashcards
internal rotators of the knee
sartorius
gracilis
semimembranosus
semitendonosous
popliteus
external rotators of the knee
biceps femoris
muscles that cross the knee innervated by the femoral nerve
sartorious
quadriceps (all)
muscles that cross the knee innervated by the tibial nerve
popliteus
gastroc
plantaris
muscles that cross the knee innervated by the sciatic nerve
semimembranosous
semitendinosous
biceps femoris
knee flexors
SM
ST
biceps femoris
sartorius
gracilis
gastroc
plantaris
popliteus
the knee and associated ligaments are supplied by what nerves
L3-L5 spinal nerve roots via posterior tibial, obturator, and femoral nerves
the larges afferent to the knee is what
posterior tibial
innervated psoterior capsule, associated ligaments, and most internal structures up to the infrapatellar fat pad
afferent fibers in teh obturator nerve carry sensation from where
skin over medial knee and post/posy-medial capsule
afferent fibers in the femoral nerve carry sensation from where
anterior medial and anaterior lateral capsule
describe the cross sectional area of the quads
as high as 2.8 x greater than hamstrings
describe the percentage of knee extension torque
vastus group = 80% total extension
rectus femoris = 20%
where does rectus femoris run
AIIS and immediately superior to acetabulum
which quad muscle has the greatest CSA
vastus lateralis
which quad muscle extends farthest distally
vastus medialis
extends fartehr toward knee
has 2 sections
where is articularis genu
deep to vastis intermed.
runs distally into capsule/synovial membrane (pulls them proximally during ext)
how much force is the knee extensor mechanism via patellar tendon capable fo producing/trasnferring
estimated in a trained young male at 6000N (1350 lbs)
knee ext torque is 2/3 > than flexors
isometric function of knee extensors
stabilizes to protect knee
eccentric function of quads
controls rate of descent of body’s COM
dampens impact/loading on knee
controls knee flexion from heel contact into loading of knee flexion in response to GRF
concentric functions of quads
accelerates tibia/femur toward ext
raises COG with jump, step up, running uphill, etc
when are external torques relatively large for open vs closed chain knee ext
90-45 degrees for femoral on tibial
45-0 for tibia on femoral
what is extensor lag
inability to complete full AROM of tibial on femoral ext
knee can be fully ext passivley
usually happens in last 15-20 degrees of ext
occurs with internal torque potential of quads is the least and external torque is the greatest
functional role of the patella
spacer between femur and quads
increases internal moment arm of extensor mechanism
greatest torque between 20-60 deg
what factors impact the length o fthe knee ext moment arm
shape/position of patella
shape of distal femur (depth and shape of trochlear groove)
migrating M-L axis - evolute
describe the joint mechanics/force in the patellofemoral joint during walking, SLR, stairs, and deep squats
walking on level surfaces = 1.3xBW
SLR = 2.6 x BW
stairs = 3.3 x BW
deep squat = up to 7.8 x BW
what are the 2 interrelated factors associated with joint compression forces on the PF joint
force within quadriceps muscle
knee flexion angle
force generation of quads in partial vs deep squat
greater force with deep due to greater external flexion torque
thus greater internal force is required
how does greater knee flexion affect the force at the patellofemoral joint
greater flexion decreases angle between quads tendon and patellar tendon and thus produces a greater joint force between patella and femur
where is max force of patellofemoral joint
60-90 deg flexion
describe the line of pull of the quads
posterior lateral
net lateral pull is indicated by Q angle
larger Q angle means larger whar
greater lateral muscle pull on patella
Q angle is formed by
quads and patella tendon (on tibia)
13-15 degrees is normal
describe patellofemoral pain syndrome
30% females, 20% male
young/active people
pain with any flexion/prolonged flexion activities
traditional treatment for abnormal tracking/dislocation of PF joint
address underlying pathomechanics
exercises:
-strengthen/control hip ABD/ER
-quads
-support foot longitudinal arch
stretch tight structures like ITB
mobilize/brace patella
reduce load at PF joint and/or quad torque
muscles that flex and rotate knee
hamstrings
sartorius
gracilis
popliteus
medial knee stabilizers that resist knee ER and also internally rotate knee
sartorius and gracilis
function of popliteus
unlocks knee by laterally RT femur on tibia during closed chain movement
medially RT knee with open chain movement (IR and flexion)
greatest leverage at the knee is during what degree of flexion
50-90
at 80 biceps femoris has a 3x greater moment arm than the average of all the internal rotators of the knee
max torque production at the knee is when
last 20 degrees of ext
flexing the hip and stretching hamstrings increases torque
