Lecture 9: Knee Musculature

Question 1

internal rotators of the knee

Answer 1

sartorius
gracilis
semimembranosus
semitendonosous
popliteus

Question 2

external rotators of the knee

Answer 2

biceps femoris

Question 3

muscles that cross the knee innervated by the femoral nerve

Answer 3

sartorious
quadriceps (all)

Question 4

muscles that cross the knee innervated by the tibial nerve

Answer 4

popliteus
gastroc
plantaris

Question 5

muscles that cross the knee innervated by the sciatic nerve

Answer 5

semimembranosous
semitendinosous
biceps femoris

Question 6

knee flexors

Answer 6

SM
ST
biceps femoris
sartorius
gracilis
gastroc
plantaris
popliteus

Question 7

the knee and associated ligaments are supplied by what nerves

Answer 7

L3-L5 spinal nerve roots via posterior tibial, obturator, and femoral nerves

Question 8

the larges afferent to the knee is what

Answer 8

posterior tibial

innervated psoterior capsule, associated ligaments, and most internal structures up to the infrapatellar fat pad

Question 9

afferent fibers in teh obturator nerve carry sensation from where

Answer 9

skin over medial knee and post/posy-medial capsule

Question 10

afferent fibers in the femoral nerve carry sensation from where

Answer 10

anterior medial and anaterior lateral capsule

Question 11

describe the cross sectional area of the quads

Answer 11

as high as 2.8 x greater than hamstrings

Question 12

describe the percentage of knee extension torque

Answer 12

vastus group = 80% total extension

rectus femoris = 20%

Question 13

where does rectus femoris run

Answer 13

AIIS and immediately superior to acetabulum

Question 14

which quad muscle has the greatest CSA

Answer 14

vastus lateralis

Question 15

which quad muscle extends farthest distally

Answer 15

vastus medialis

extends fartehr toward knee

has 2 sections

Question 16

where is articularis genu

Answer 16

deep to vastis intermed.

runs distally into capsule/synovial membrane (pulls them proximally during ext)

Question 17

how much force is the knee extensor mechanism via patellar tendon capable fo producing/trasnferring

Answer 17

estimated in a trained young male at 6000N (1350 lbs)

knee ext torque is 2/3 > than flexors

Question 18

isometric function of knee extensors

Answer 18

stabilizes to protect knee

Question 19

eccentric function of quads

Answer 19

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

Question 20

concentric functions of quads

Answer 20

accelerates tibia/femur toward ext

raises COG with jump, step up, running uphill, etc

Question 21

when are external torques relatively large for open vs closed chain knee ext

Answer 21

90-45 degrees for femoral on tibial

45-0 for tibia on femoral

Question 22

what is extensor lag

Answer 22

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

Question 23

functional role of the patella

Answer 23

spacer between femur and quads

increases internal moment arm of extensor mechanism

greatest torque between 20-60 deg

Question 24

what factors impact the length o fthe knee ext moment arm

Answer 24

shape/position of patella

shape of distal femur (depth and shape of trochlear groove)

migrating M-L axis - evolute

Question 25

describe the joint mechanics/force in the patellofemoral joint during walking, SLR, stairs, and deep squats

Answer 25

walking on level surfaces = 1.3xBW

SLR = 2.6 x BW

stairs = 3.3 x BW

deep squat = up to 7.8 x BW

Question 26

what are the 2 interrelated factors associated with joint compression forces on the PF joint

Answer 26

force within quadriceps muscle

knee flexion angle

Question 27

force generation of quads in partial vs deep squat

Answer 27

greater force with deep due to greater external flexion torque

thus greater internal force is required

Question 28

how does greater knee flexion affect the force at the patellofemoral joint

Answer 28

greater flexion decreases angle between quads tendon and patellar tendon and thus produces a greater joint force between patella and femur

Question 29

where is max force of patellofemoral joint

Answer 29

60-90 deg flexion

Question 30

describe the line of pull of the quads

Answer 30

posterior lateral

net lateral pull is indicated by Q angle

Question 31

larger Q angle means larger whar

Answer 31

greater lateral muscle pull on patella

Question 32

Q angle is formed by

Answer 32

quads and patella tendon (on tibia)

13-15 degrees is normal

Question 33

describe patellofemoral pain syndrome

Answer 33

30% females, 20% male

young/active people

pain with any flexion/prolonged flexion activities

Question 34

traditional treatment for abnormal tracking/dislocation of PF joint

Answer 34

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

Question 35

muscles that flex and rotate knee

Answer 35

hamstrings
sartorius
gracilis
popliteus

Question 36

medial knee stabilizers that resist knee ER and also internally rotate knee

Answer 36

sartorius and gracilis

Question 37

function of popliteus

Answer 37

unlocks knee by laterally RT femur on tibia during closed chain movement

medially RT knee with open chain movement (IR and flexion)

Question 38

greatest leverage at the knee is during what degree of flexion

Answer 38

50-90

at 80 biceps femoris has a 3x greater moment arm than the average of all the internal rotators of the knee

Question 39

max torque production at the knee is when

Answer 39

last 20 degrees of ext

flexing the hip and stretching hamstrings increases torque