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Biomechanics Exam 2 > KNEE > Flashcards

KNEE Flashcards

1
Q

muscles of pes anserinus

A

-sartorius
-gracilis
-semitendinosus

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2
Q

anterior + posterior shear forces in knee extension

A

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

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3
Q

anterior + posterior shear forces in 45 degrees knee flexion

A

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

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4
Q

anteiror + posterior shear forces in 90 degrees knee flexion

A

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

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5
Q

patellofermoral joint

A

articulation between patella + patellar groove of femur

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6
Q

least congruent joint in the body

A

patellofemoral

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7
Q

patella functions

A

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

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8
Q

patellar compression force

A

-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

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9
Q

describe the obliquity of pull of knee

A

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

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10
Q

what type of joint is tibiofemoral joint (knee joint)

A

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

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11
Q

articular surfaces of tibiofemoral joint

A

convex: femur
concave: tibial plateau

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12
Q

what femoral condyle is larger

A

medial

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13
Q

what side of tibia is larger

A

medial

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14
Q

describe congruence of tibiofemoral joint

A

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

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15
Q

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

A

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.

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16
Q

how many main df of knee

A

2
-flexion/extension
-medial/lateral rotation

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17
Q

flexion arthrokinematics

A

posterior roll FIRST, then anterior glide

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18
Q

extension arthrokinematics

A

anterior roll FIRST, then posterior glide

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19
Q

when is axial (medial/lateral) rotation accessible

A

only in knee flexion

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20
Q

external rotation arthrokinematics

A

posterior glide of lateral femoral condyle on tibia

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21
Q

internal rotation arthrokinematics

A

anterior glide of lateral femoral condyle on tibia

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22
Q

genu valgum

A

knock knee, knee abduction

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23
Q

where does mechanical axis pass through for genu valgum

A

lateral side

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24
Q

genu valgum has excess compressive loading on which side of knee

A

lateral
-increased force on lateral condyle

25
Q

genu varum

A

bow legged, knee adduction

26
Q

where does mechanical axis for genu varum pass through

A

medial side

27
Q

genu varum has excess compressive loading on which side of knee

A

medial
-increased force on medial condyle

28
Q

Q-angle

A

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

29
Q

Q-angle is larger in which 2 cases

A

-genu valgum
-femoral anteversion

30
Q

larger Q-angle causes what risk factor

A

ACL tear

31
Q

what are the menisci made of

A

fibrocartilage

32
Q

describe the thickening of the menisci

A

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

33
Q

menisci functions

A

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

34
Q

what type of stress do the menisci reduce

A

compressive

35
Q

collateral ligaments

A

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

36
Q

cruciate ligaments

A

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

37
Q

ACL primary function

A

resist anterior translation of tibia

38
Q

ACL lesser functions

A

-resist varus/valgus stress
-prevent excess hyperextension

39
Q

when is the ACL commonly torn

A

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

40
Q

PCL primary function

A

resists posterior translation of tibia

41
Q

PCL lesser functions

A

resists varus/valgus stress

42
Q

differentiating ACL from PCL

A

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

43
Q

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

A

ACL wraps around PCL

44
Q

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

A

ACL wraps around lateral femoral condyle, causing it to rupture

45
Q

MCL primary function

A

resists valgus stress

46
Q

MCL lesser function

A

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

47
Q

MCL special feature

A

posterior medial fibers blend with joint capsule

48
Q

LCL primary function

A

resists varus stress

49
Q

LCL special feature

A

strong + cordlike

50
Q

oplique popliteal ligament primary function

A

resists hyperextension + valgus stress in full knee extension

51
Q

what is the joint capsule of oblique popliteal ligament reinforced by

A

tendinous expansion of semimembranosus

52
Q

arcuate ligament primary function

A

resists hyperextension + varus stress in full knee extension

53
Q

when are the oblique popliteal ligament + arcuate ligament taut

A

extension

54
Q

screw home mechanism

A

-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

55
Q

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

A

-locks via passive
-unlocks via active

56
Q

what is the screw home mechanism caused by

A

asymmetry in medial + lateral femoral condyles
-medial is larger

57
Q

what muscle unlocks the knee

A

popliteus

58
Q

describe the unlocking of the knee

A

-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

Biomechanics Exam 2 (4 decks)

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