KNEE

Question 1

muscles of pes anserinus

Answer 1

-sartorius
-gracilis
-semitendinosus

Question 2

anterior + posterior shear forces in knee extension

Answer 2

-smallest hamstring posterior shear force
-largest quad anterior shear force

Question 3

anterior + posterior shear forces in 45 degrees knee flexion

Answer 3

-medium hamstrings force, growing posterior shear force
-medium quad force, small anterior shear force

Question 4

anteiror + posterior shear forces in 90 degrees knee flexion

Answer 4

-largest hamstring posterior shear force
-vertical quad force, no anterior shear force

Question 5

patellofermoral joint

Answer 5

articulation between patella + patellar groove of femur

Question 6

least congruent joint in the body

Answer 6

patellofemoral

Question 7

patella functions

Answer 7

-pulley
-reduces friction between quadriceps tendon + femoral condyles
-improves mechanical advantage of knee extensors
-increases moment arm + therefore quadriceps torque

Question 8

patellar compression force

Answer 8

-as knee flexion increases, the pull of quads + patellar ligament become increasingly oblique, compressing patella into femur
-so resultant force of patella increases with knee flexion

Question 9

describe the obliquity of pull of knee

Answer 9

-resultant vector acting on patella is lateral
-because determined by line of action of quadriceps tendon + patellar ligament

Question 10

what type of joint is tibiofemoral joint (knee joint)

Answer 10

-modified hinge (because flexion/extension)
-double condyloid
(because convex/concave)

Question 11

articular surfaces of tibiofemoral joint

Answer 11

convex: femur
concave: tibial plateau

Question 12

what femoral condyle is larger

Answer 12

medial

Question 13

what side of tibia is larger

Answer 13

medial

Question 14

describe congruence of tibiofemoral joint

Answer 14

low congruence
-due to small concavity of tibial condyles vs large convexity of femoral condyles

Question 15

how do we compensate for lack of bony congruence in the knee

Answer 15

we rely on soft tissue for knee stability
-depends on dynamic + static soft tissue restraints

-dynamic restraints: quadriceps, hamstrings, gastroc, etc.
-static restraints: joint capsule, menisci, ligaments, etc.

Question 16

how many main df of knee

Answer 16

2
-flexion/extension
-medial/lateral rotation

Question 17

flexion arthrokinematics

Answer 17

posterior roll FIRST, then anterior glide

Question 18

extension arthrokinematics

Answer 18

anterior roll FIRST, then posterior glide

Question 19

when is axial (medial/lateral) rotation accessible

Answer 19

only in knee flexion

Question 20

external rotation arthrokinematics

Answer 20

posterior glide of lateral femoral condyle on tibia

Question 21

internal rotation arthrokinematics

Answer 21

anterior glide of lateral femoral condyle on tibia

Question 22

genu valgum

Answer 22

knock knee, knee abduction

Question 23

where does mechanical axis pass through for genu valgum

Answer 23

lateral side

Question 24

genu valgum has excess compressive loading on which side of knee

Answer 24

lateral
-increased force on lateral condyle

Question 25

genu varum

Answer 25

bow legged, knee adduction

Question 26

where does mechanical axis for genu varum pass through

Answer 26

medial side

Question 27

genu varum has excess compressive loading on which side of knee

Answer 27

medial -increased force on medial condyle

Question 28

Q-angle

Answer 28

angle between line 1 (center of patella to ASIS) + line 2 (patella to tibial tuberosity)

Question 29

Q-angle is larger in which 2 cases

Answer 29

-genu valgum -femoral anteversion

Question 30

larger Q-angle causes what risk factor

Answer 30

ACL tear

Question 31

what are the menisci made of

Answer 31

fibrocartilage

Question 32

describe the thickening of the menisci

Answer 32

thins out as you move into the knee joint space + thickens peripherally

Question 33

menisci functions

Answer 33

-increase contact surface area -distribute weight bearing loads -shock reabsorption, reduce compressive stress -reduce friction

Question 34

what type of stress do the menisci reduce

Answer 34

compressive

Question 35

collateral ligaments

Answer 35

cross medial + lateral aspects of the knee -MCL -LCL

Question 36

cruciate ligaments

Answer 36

cross eachother in connecting anterior + posterior aspects of the knee -ACL -PCL

Question 37

ACL primary function

Answer 37

resist anterior translation of tibia

Question 38

ACL lesser functions

Answer 38

-resist varus/valgus stress -prevent excess hyperextension

Question 39

when is the ACL commonly torn

Answer 39

knee flexion with valgus + either direction of tibia rotation -also hyperextension

Question 40

PCL primary function

Answer 40

resists posterior translation of tibia

Question 41

PCL lesser functions

Answer 41

resists varus/valgus stress

Question 42

differentiating ACL from PCL

Answer 42

-ACL smaller than PCL -ACL more horizontal looking -PCL more vertical looking

Question 43

describe what ACL does in knee flexion, valgus, lateral femoral rotation

Answer 43

ACL wraps around PCL

Question 44

describe what ACL does in knee flexion, valgus, medial femoral rotation

Answer 44

ACL wraps around lateral femoral condyle, causing it to rupture

Question 45

MCL primary function

Answer 45

resists valgus stress

Question 46

MCL lesser function

Answer 46

backup restraint to preventing anterior translation of tibia when ACL is deficient

Question 47

MCL special feature

Answer 47

posterior medial fibers blend with joint capsule

Question 48

LCL primary function

Answer 48

resists varus stress

Question 49

LCL special feature

Answer 49

strong + cordlike

Question 50

oplique popliteal ligament primary function

Answer 50

resists hyperextension + valgus stress in full knee extension

Question 51

what is the joint capsule of oblique popliteal ligament reinforced by

Answer 51

tendinous expansion of semimembranosus

Question 52

arcuate ligament primary function

Answer 52

resists hyperextension + varus stress in full knee extension

Question 53

when are the oblique popliteal ligament + arcuate ligament taut

Answer 53

extension

Question 54

screw home mechanism

Answer 54

-refers to the OBLIGATORY locking of the knee, seen in the last few degrees of extension -in the last few degrees of extension, the lateral condyle must terminate rolling/gliding while the medial condyle continues to roll/glide -this causes medial rotation of femur

Question 55

-the knee locks via passive/active mechanics -the knee locks via passive/active mechanics

Answer 55

-locks via passive -unlocks via active

Question 56

what is the screw home mechanism caused by

Answer 56

asymmetry in medial + lateral femoral condyles -medial is larger

Question 57

what muscle unlocks the knee

Answer 57

popliteus

Question 58

describe the unlocking of the knee

Answer 58

-occurs in initial degrees of flexion -closed chain: medially rotated femur must laterally rotate to initiate flexion -closed chain: laterally rotated tibia must medially rotate to initiate flexion