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Lower Extremity Anatomy And Biomechanics > Knee Biomechanics > Flashcards

Knee Biomechanics Flashcards

1
Q

What type of joint is the knee?

A

a modified ginglymus joint

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2
Q

What bones are all involved in the knee?

A

femur, tibia and patella

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3
Q

Is the knee part of the OKC or CKC?

A

it is part of the closed kinetic chain system

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4
Q

What are the movements provided by the knee?

A

flexion and extension

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5
Q

What are the two separate types of joints in the knee?

A
  • Tibiofemoral joint

- Patellofemoral joint

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6
Q

Describe the tibiofemoral joint? What does it articulate with and what is between each surface?

A
  • proximal tibia articulates with the distal femur

- meniscus is between the two surfaces

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7
Q

Describes what articulates with the patellofemoral joint?

A

articulation of the posterior surface of the patella and the trochlear surface of the anterior femur

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8
Q

Describe the Q-angle? What is the alignment and the landmarks?

A
  • alignment at the patellofemoral joint

- landmarks: line connecting the ASIS to the midpoint of the patella, and a line to the tibial tuberosity

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9
Q

What portion of the knee has increased pressure with a smaller Q-angle?

A

medial knee pressure is increased

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10
Q

What portion of the knee has increased pressure with a larger Q-angle?

A

Lateral knee pressure is increased

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11
Q

What is genu valgum?

A

knocked kneed

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12
Q

Where is the increase compression for knee with genu valgum? How much can genu valgum ambulation increase compression forces?

A
  • increase compression in lateral compartment of knee (increased chance of OA)
  • by 2.5-3.0 multiplied by your body weight
  • causes mechanical breakdown of components in lateral compartment
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13
Q

What knee angle is excessive for genu valgum?

A

greater than 190 degrees is excessive

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14
Q

What angle is normal for genu valgum?

A

5-10 degrees is normal

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15
Q

What is genu varum?

A

bow legged

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16
Q

What is the knee angle for genu varus?

A

knee angle less than 170 degrees

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17
Q

Where is the increase compression for knee with genu varum?

A

increased compression in medial compartment of knee

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18
Q

What can “theoretically” predispose genu varum?

A
  • coxa vara femoral neck-shaft (angle less than 125 degrees)

- weaken hip muscle, particularly the hip abductors (glute med)

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19
Q

What is Genu recuvatum? Describe its position?

A
  • extension beyond +10 of neutral
  • area of condyles in contact during end range extension is decreased, resulting in increased compressive forces secondary to smaller area
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20
Q

What are the functions of the proximal tibiofibular joint?

A
  • dissipation of torsional stresses applied at the ankle
  • dissipation of lateral tibial bending movements
  • tensile weight bearing
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21
Q

Where does movement occur for the proximal tibiofibular joint?

A

at the ankle

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22
Q

What type of joint is the tibiofemoral joint?

A

double condyloid synovial joint

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23
Q

How many degrees of freedom does the tibiofemoral joint have?

A

3 degrees of freedom

  • flex/extend
  • IR/ER
  • Abd/Add
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24
Q

Extension-Tibia on femur: open chain

A

anterior roll anterior glide

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25
Q

Flexion-Tibia on femur: open chain

A

posterior roll posterior glide

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26
Q

Extension-femur on tibia: closed chain

A

anterior roll posterior glide

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27
Q

Flexion-femur on tibia: closed chain

A

posterior roll anterior glide

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28
Q

When does the screw-home mechanism occur and why does it occur?

A
  • occurs in the final 20-30 degrees of knee extension

- due to the shape and size of the medial condyle

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29
Q

What does the ACL all resist against?

A
  • resists against knee extension
  • helps prevent hyperextension (recurvatum)
  • excessive tibial anterior slide
  • excessive femoral posterior slide
  • excessive axial rotation, varus and valgus forces
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30
Q

Where does the ACL attach?

A

to the anterior tibia and runs in a posterior, lateral and proximal direction attaching to the lateral femoral condyle

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31
Q

Describe the chain of events for extension (the screw-home) when foot is planted with knee flexed?

A
  • The ACL becomes tight
  • ACL tightness restricts movement of the lateral femoral condyle
  • the medial condyle is not restricted so it keeps moving
  • causes tibial ER, femoral IR
  • this locks the knee at full extension
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32
Q

What does the popliteus do during flexion of the knee?

A

unlocks the knee and causes the tibia to medially rotate

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33
Q

What is the closed packed position for tibiofemoral joint?

A

full extension with ER

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34
Q

What is open packed position for tibiofemoral joint?

A

25-30 degrees of knee flexion

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35
Q

What is the capsular pattern for tibiofemoral joint?

A

flexion > extension

36
Q

What is the importance of the patellofemoral joint?

A
  • increases angle of insertion for the quads

- increases the torque producing capability for the quads

37
Q

Arthrokinematics for patella moving on femur

A

patella slides along fixed intercondylar groove

38
Q

Arthrokinematics for femur moving on patella

A

intercondylar groove slides along fixed patella

39
Q

What are the gliding motions of the patellofemoral joint?

A
  • flexion/extension (superior and inferior glides)
  • medial and lateral glides
  • medial and lateral tilts
  • medial and lateral rotation
  • anterior and posterior tilts
40
Q

What is patella alta?

A

high-riding patella

41
Q

What is patella baja?

A

low-riding patella

42
Q

What kind of joint is the poximal tibiofibular joint? and describe the shapes of articulations

A
  • plane synovial joint

- fibula is slightly convex, tibia is slightly concave

43
Q

How many degrees of freedom does the proximal tibiofibular joint have?

A
  • 3 DOF (gliding motions)
  • anterior/posterior
  • superior/inferior
  • rotation
44
Q

What is the closed packed position for the proximal tibiofibular joint?

A

full ankle dorsiflexion

45
Q

What is the open packed position for the proximal tibiofibular joint?

A

0 degrees plantar flexion

46
Q

What is the capsular pattern for the proximal tibiofibular joint?

A

pain with biceps femoris muscle contraction

47
Q

What causes lateral patellar tracking?

A
  • ITB
  • bowstringing
  • lateral patellar retinacular fibers
48
Q

What causes medial patellar tracking?

A
  • VMO
  • raised lateral facet
  • medial patellar retinacular fibers
49
Q

What can a valgus external force cause on the knee to patella and knee itself?

A
  • causes ER of the femur and IR of tibia
  • increases tension at QT and PT and increases bowstringing force
  • it results in increased lateral displacement of patella
50
Q

What are the 3 bands of the ACL?

A

anteromedial, intermedial, and posterolateral

51
Q

In knee extension, which bands are tight/slack for ACL?

A
  • anteromedial band is slack

- posterolateral band is tight

52
Q

In knee flexion, which bands are tight/slack for ACL?

A
  • anteromedial band is tight

- posterolateral band is slack

53
Q

How do you injure the ACL? besides cutting it off with a saw

A
  • large valgus force with foot planted
  • large axial rotation force applied with foot planted
  • combination of previous 2
  • severe hyperextension
54
Q

Where does the PCL attach?

A

posterior tibia and runs in a proximal, medial and anterior direction attaching to the medial femoral condyle

55
Q

What does the PCL resist against? When is it most effective (flex/extend)?

A
  • excessive tibial posterior slide
  • excessive femoral anterior slide
  • excessive femoral axial rotation, varus and valgus forces
  • most effective in flexion
56
Q

How do you injure the PCL?

A
  • falling on fully flexed knee with proximal tibia striking first
  • force posterior translation of tibia
  • worse with increasing flexion
  • rotation, varus, and/or valgus force applied with foot planted
  • severe hyperextension with gapping to posterior side
57
Q

Where does the superficial MCL attach?

A

-proximally to the medial femoral epicondyle and distally at the shaft of the tibia and tibial condyle

58
Q

Where does the deep portion MCL attach?

A

attachment to the medial meniscus and blends with the knee joint capsule

59
Q

What is the function of the MCL?

A
  • resist valgus force
  • resist knee extension
  • reinforce medial capsule
  • prevent ER of the leg with the knee extended
60
Q

How do you injure the MCL

A
  • valgus producing force with foot planted

- severe hyperextension

61
Q

Where does the LCL attach?

A

runs from the lateral epicondyle of the femur to the head of the fibula
-DOES NOT attach to the meniscus

62
Q

What is the function of the LCL?

A
  • resist varus force
  • resist knee extension
  • prevent ER of the leg with knee extended
  • reinforce lateral capsule
  • reinforce posterior-lateral capsule
63
Q

How do you injure the LCL?

A
  • varus producing force with foot planted

- severe hyperextension

64
Q

What all reinforces the joint capsule anteriorly ?

A
  • muscle-tendinous: quads

- connective tissue: patellar tendon and patellar retinacular fibers

65
Q

What does the joint capsule encompass?

A

both compartments of the tibiofemoral joint and the patellofemoral joint

66
Q

What all reinforces the joint capsule laterally ?

A
  • Connective tissue: LCL, lateral retinaculum, IT band

- muscular tendinous: biceps femoris, popliteus, gastrocnemius

67
Q

What all reinforces the joint capsule posteriorly?

A
  • connective tissue: oblique popliteal ligament and arcuate complex
  • muscular-teninous: gastrocnemius and hamstring group
68
Q

What all reinforces the joint capsule posterior-laterally ?

A

Connective tissue: arcuate complex and LCL

muscular-tendinous: popliteus

69
Q

What all reinforces the joint capsule medially?

A
  • connective tissue: retinaculum, MCL, posterior-medial capsule, and posterior oblique ligament
  • muscular-teninous: pes anserine
70
Q

What are the functions of the meniscus?

A
  • deepen the surface of the tibia
  • makes a concavity atop the tibial plateau
  • shock absorbers
71
Q

What is the meniscus and where are the located?

A
  • fibrocartilaginous discs

- located directly between the femoral condyles and the tibial plateau

72
Q

Describe the medial meniscus?

A
  • larger and more C-shaped

- has anterior and posterior horns

73
Q

What attaches to the medial meniscus?

A
  • MCL and medial capsule

- posteriorly attaches to the semimembranosus

74
Q

Is the medial or lateral meniscus injured more frequently and why?

A

-medial injured more frequently because of firm attachment of the tibia and decrease mobility

75
Q

Describe the lateral meniscus and its function?

A
  • more circular shaped
  • loosely attached to the tibia
  • absorbs more of the stress
76
Q

Is the medial or lateral meniscus more mobile?

A

lateral and less susceptible to injury

77
Q

What does the lateral meniscus attach to?

A

posteriorly attaches to the popliteus

78
Q

What happens to the menisci during knee extension?

A

-move anteriorly with the tibia

79
Q

What happens to the menisci during knee flexion?

A

-move posterior with the tibia

80
Q

How do you injure the meniscus?

A
  • axial rotation, values force most common MOI

- injury can be correlated with early onset OA

81
Q

What percent of ACL tears are associated with meniscal injury?

A

50%

82
Q

What is the function of bursae?

A

reduces friction between moving structures

83
Q

Where is the infra patellar fat pad and what is its function?

A
  • between the patellar tendon and the tibia (very sensitive)

- helps reduce friction in the knee

84
Q

What is active insufficiency?

A
  • extreme shortened muscle results in decreased motor recruitment
  • must shorten over both joint
85
Q

What is passive insufficiency?

A

-tightened/lengthened muscles causes decreased muscle contraction

86
Q

Describe the length tension relationship?

A

-muscles at full contraction or extension lose contractile capabilities

Lower Extremity Anatomy And Biomechanics (12 decks)

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