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Biomechanics > Knee > Flashcards

Knee Flashcards

1
Q

What does the knee consist of?

A

lateral and medial compartments of tibiofemoral joint and patellofemoral joint

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2
Q

What are the motions of the knee?

A

flexion and extension

internal and external rotation

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3
Q

The shaft of femur angles slightly _____ as it descends toward knee

A

medially

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4
Q

The oblique orientation is a result of natural _____ angle of inclination or proximal femur

A

125 degrees

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5
Q

Why does the knee form an angle in its lateral side of about 170-175 degrees?

A

Because articular surface pf proximal tibia is oriented nearly horizontally

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6
Q

Normal alignment of knee within frontal plane is referred to as:

A

genu valgum

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7
Q

Excessive genu valgum or knock-knee:

A

lateral angle less that 170 degrees

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8
Q

Genu Varum or bow leg:

A

lateral angle greater than 180 degrees

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9
Q

Longitudinal or vertical axis of rotation at hip defined as what:

A

line connecting femoral head with center of knee joint

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10
Q

What does the tibiofemoral joint consist of?

A

articulations between large convex femoral condyles and nearly flat smaller tibial condyles

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11
Q

Large articular surface area of femoral condyles permits:

A

extensive knee motion in sagittal plane for activities such as running, squatting and climbing

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12
Q

What is joint stability provided by?

A

forces and physical containment provided by muscles, ligaments, capsule, menisci and body weight

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13
Q

The transformation of the lateral mensici into shallow seat for femoral condyle is most important because:

A

flat to slightly convex shape of tibia’s lateral articular surface

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14
Q

What anchors menisci to intercondylar region of tibia?

A

free ends, known as anterior and posterior horns

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15
Q

External edge of each meniscuc attached to tibia and adjacent capsule by what?

A

coronary (or meniscotibial) ligaments

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16
Q

What do the coronary ligaments allow menisci to pivot freely during movement?

A

because the coronary ligaments are relatively loose

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17
Q

What connects both menisci anteriorly?

A

transverse ligament

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18
Q

What muscles attach to both menisci?

A

quads and semimembranosus

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19
Q

What muscle attaches to lateral meniscus?

A

popliteus

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20
Q

What helps to stabilize the position of menisci?

A

muscle attachments

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21
Q

Where is blood supply of the menisci greatest?

A

near peripheral (external) border

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22
Q

Internal border of menisci is essentially:

A

avascular

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23
Q

Where is blood from capillaries located within:

A

adjacent synovial membrane and capsule

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24
Q

The shape of the medial meniscus is:

A

oval shape

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25
Q

The shape of the lateral meniscus is:

A

circular shape

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26
Q

External border of the medial meniscus attaches to:

A

to deep surface of MCL and adjacent capsule

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27
Q

External border of the lateral meniscus attaches:

A

only to lateral capsule

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28
Q

What passes between LCL and external border of lateral meniscus?

A

tendon of popliteus

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29
Q

What is the primary function of menisci?

A

reduce compressive stress across tibiofemoral joint

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30
Q

What are other functions of menisci?

A

Stabilizing joint during motion
Lubricating articular cartilage
Providing proprioception
Helping to guide knee’s arthrokinematics

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31
Q

Br tripling area of joint contact, menisci significantly ______ pressure on articular cartilage

A

decrease

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32
Q

Complete lateral meniscecetomy increases:

A

contact pressure at knee by 230%

increases risk of developing stress related OA

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33
Q

What is the most common injury of the knee?

A

tears of meniscus

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34
Q

What are meniscal tears associated with?

A

forceful axial rotation of femoral condyles over partially flexed and weight-bearing knee

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35
Q

What can pinch and dislodge meniscus?

A

Axial torsion within compressed knee

36
Q

What is a bucket-handle tear?

A

Dislodged or folded flap of meniscus that can mechanically block knee movement

37
Q

What is the MOI for medial meniscus?

A

axial rotation and external valgus force applied to lateral aspect of knee

38
Q

What can valgus force cause?

A

subsequent large stress on MCL and posterior-medial capsule

39
Q

How many degrees of freedom does the tibifemoral joint posses?

A

two degrees of freedom:
flexion and extension (sagittal plane)
internal and external rotation (provided knee slightly flexed)

40
Q

When does frontal plane motion at the knee occur?

A

passively only limited to 6-7 degrees

41
Q

The ML axis or rotation for flexion and extension is not fixed but migrates with:

A

femoral condyles

42
Q

The curved path of axis is known as:

43
Q

The Path of axis influenced by:

A

eccentric curvature of femoral condyles

44
Q

The migrating AOR does what two things:

A
  • alters length of internal moment arm of flexor and extensor muscles of knee
  • external devices that attach to the knee rotate about fixed axis of rotation
45
Q

Internal and external rotation occurs about a:

A

vertical or longitudinal axis of rotation

also called axial rotation

46
Q

Freedom of axial rotation increases with:

A

greater knee flexion

47
Q

When the knee is flexed to 90 degrees:

A

about 40-45 degrees of total axial rotation

48
Q

External rotation range of motion generally exceeds internal rotation by ratio of about:

49
Q

When is axial rotation maximally restricted:

A

once knee is in full extension

50
Q

What is rotation blocked by:

A

passive tension in stretched ligaments, capsule, and increased bony congruity within joint

51
Q

During tibial-on-femoral extension, articular surface of tibia:

A

rolls and slides anteriorly on femoral condyles

52
Q

During femoral-on-tibial extension (standing up from deep squat)

A

femoral condyles simultaneously roll anteriorly and slide posteriorly on articular surface of tibia

53
Q

What directs roll of femoral condyles and stabilizes menisci against horizontal shear caused by sliding femur?

54
Q

What does the locking of knee in full extension require?

A

10 degrees of external rotation

55
Q

What is the screw home mechanism?

A

Rotary locking action

rotation observable during 30 degrees of extension

56
Q

For knee that is fully extended to be unlocked the joint must first:

A

internally rotate

57
Q

What muscle drives the internal rotation of the knee?

58
Q

What can the popliteus muscle do?

A

rotate femur externally to initiate femoral-on-tibial flexion or can rotate tibia internally to initiate tibial-on-femoral flexion

59
Q

What position must the knee be in to maximize independent axial rotation b/w tibia and femur?

60
Q

What is the function of the MCL (and posterior-medial capsule):

A
  1. Resists valgus (abduction)
  2. Resists knee extension
  3. Resists extremes of axial rotation (especially knee external rotation)
61
Q

What is the common MOI of MCL (and posterior-medial capsule):

A
  1. Valgus-producing force with foot planted (e.g., “clip” in football)
  2. Severe hyperextension of knee
62
Q

What is the function of the LCL?

A
  1. Resists varus (adduction)
  2. Resists knee extension
  3. Resists extremes of axial rotation
63
Q

What is the common MOI of the LCL?

A
  1. Varus-producing force with foot planted

2. Severe hyperextension of knee

64
Q

What is the function of the ACL?

A
  1. Most fibers resist extension (either excessive anterior translation of tibia, posterior translation of femur, or a combination thereof)
  2. Resists extremes of varus, valgus, and axial rotation
65
Q

What is the common MOI of the ACL?

A
  1. Large valgus-producing force with foot firmly planted
  2. Large axial rotation torque applied to knee (in either rotation direction), with foot firmly planted
  3. Any combination of above, especially involving strong quadriceps contraction with knee in full or near-full extension
  4. Severe hyperextension of knee
66
Q

What is the function of the PCL?

A
  1. Most fibers resist knee flexion (either excessive posterior translation of tibia or anterior translation of femur, or a combination thereof)
  2. Resists extremes of varus, valgus, and axial rotation
67
Q

What is the common MOI of the PCL?

A
  1. Falling on fully flexed knee (with ankle fully plantar flexed) such that proximal tibia first strikes ground
  2. Any event that causes forceful posterior translation of tibia (i.e., “dashboard” injury) or anterior translation of femur, especially while knee is flexed
  3. Large axial rotation or valgus-varus applied torque to knee with foot firmly planted, especially while knee is flexed
  4. Severe hyperextension of knee causing a large gapping of posterior side of joint
68
Q

Approximately 70% of ACL sporting-related injuries occur through what?

A

non-contact or minimal contact

69
Q

Muscles of the knee describes asL

A
  • knee extensors

- knee flexor-rotators

70
Q

Sartorius action:

A

Hip flexion, external rotation, and abduction

Knee flexion and internal rotation

71
Q

Gracilis action:

A

Hip flexion and adduction

Knee flexion and internal rotation

72
Q

Quads action:

rectus femoris and vastus group

A

Knee extension and hip flexion

Knee extension

73
Q

Popliteus action:

A

Knee flexion and internal rotation

74
Q

Semimembranosus action:

A

Hip extension

Knee flexion and internal rotation

75
Q

Semitendinosus action:

A

Hip extension

Knee flexion and internal rotation

76
Q

Biceps femoris (short head) action:

A

Knee flexion and external rotation

77
Q

Biceps femoris (long head) action:

A

Hip extension

Knee flexion and external rotation

78
Q

Gastrconemius action:

A

Knee flexion

Ankle plantar flexion

79
Q

Plantaris action:

A

Knee flexion

Ankle plantar flexion

80
Q

What is external torque of the knee equal to:

A

external load being moved or supported, multiplied by its external moment arm

81
Q

When is the internal moment arm used by the quads the greatest?

A

between 60 and 20 degrees of knee flexion

82
Q

When is the internal moment arm used by the hamstrings (knee flexors) the greatest?

A

between 50-90 degrees of knee flexion

83
Q

What are the two inter-related factors associated with joint compression force on the patellofemoral joint:

A

Force within quadriceps muscle

Knee flexion angle

84
Q

The larger the Q angle, the greater:

A

lateral muscle pull on patella

85
Q

Opposing forces do what so that the patella tracks optimally during flexion and extension?

A

counteract

86
Q

What can increase the Q angle?

A

excessive knee valgus and knee external rotation

87
Q

Increased external rotation of the knee can occur as a combination of what?

A

excessive internal rotation of femur and external rotation of tibia

Biomechanics (13 decks)

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