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Biomechanics > Knee and Ankle Function > Flashcards

Knee and Ankle Function Flashcards

1
Q

Which femoral condyle deviates from the femoral midline more?

A

medial condyle

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2
Q

which condyle is longer and more narrow?

A

medial condyle

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3
Q

which condyle possibly facilitates the screw-home mechanism?

A

the longer medial condyle

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4
Q

what is the shape of the medial meniscus?

A

C-shaped

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5
Q

what is the shape of the lateral meniscus?

A

complete circle

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6
Q

what shape do the menisci appear on cross-section?

A

triangular

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7
Q

what is the function of menisci?

A

shock absorption and spacers within joint

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8
Q

in which position- flexion/extension - is the knee more stable?

A

more stable in extension than flexion

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9
Q

explain the roll and glide theory for the knee joint.

A

the femur will roll and glide during knee flexion to allow the knee to flex without impinging on the posterior tibial plateau

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10
Q

what is open kinetic chain?

A

non-weight bearing (swing phase)

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11
Q

what is closed kinetic chain?

A

WB (stance phase)

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12
Q

explain the screw-home mechanism.

A
  • external rotation of the tibia on the femur during the last 15-20 degrees of extension (OKC)
  • internal rotation of the femur (CKC)
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13
Q

in CKC, which portion is moving on which portion?

A

in CKC, the proximal segment is moving on the distal segment

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14
Q

in OKC, what portion is moving on which portion?

A

in OKC, the distal segment is moving on the proximal segment

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15
Q

what is the function of anterior thigh muscles?

A
  • extend the knee in OKC

- pull thigh over a stationary tibia in CKC

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16
Q

what is the function of lateral thigh muscles (tensor fascia lata)?

A

abducts the tibia on the femur in OKC

externally rotates the tibia on the femur in OKC

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17
Q

what is the function of posterior thigh muscles?

A

strong knee joint flexors in OKC

*hamstring muscle action ocurs mainly in swing phase (OKC)

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18
Q

which muscle group has minimal function during gait?

A

medial thigh muscles

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19
Q

what is happening during contact phases?

A
  • knee joint is flexing to absorb shock (aided by hamstrings)
  • quadriceps contract to keep knee from buckling
20
Q

what is happening during midstance phases?

A
  • quads continue to contract and extend the knee
  • when the body mass passes over the knee joint, quads are no longer needed
  • tensor fascia lata externally rotates the tibia on the femur during the last 20 degrees of knee extension
21
Q

what is happening during propulsive phase?

A
  • TFL continues to externally rotate the tibia as knee continues to extend
  • adductors contract during double support phase of gait
  • hamstrings start to fire to flex knee preparing for swing phase
22
Q

what is happening during swing phase?

A
  • hamstrings flex knee at start of swing phase to allow foot to clear the ground
  • knee extends the rest of swing phase preparing for contact (quads only needed last 20 deg of extension)
  • hamstrings contract to counteract quads and keep knee from fully extending
23
Q

which portion of the trochlea is wider?

A

anterior portion is 25% wider

24
Q

in which position is the ankle joint more stable?

A

dorsiflexed position

25
Q

in which position do most ankle sprains occur?

A

plantarflexed position

26
Q

what is the posterior part of tibial plafond called?

A

posterior malleolus

27
Q

what is the ankle joint axis?

A

8 degrees from transverse plane
20-30 degrees from frotnal plane
*motion is about the sagittal plane

28
Q

transverse plane motion at ankle reduces amount of frontal plane motion needed at STJ.

A

true

29
Q

in OKC, define dorsiflexion and plantarflexion.

A

(distal segment is moving on proximal segment in OKC)
dorsiflexion- foot moves toward tibia
plantarflexion- foot moves away from tibia

30
Q

in CKC, define dorsiflexion and plantarflexion.

A

(proximal segment is moving on distal segment in OKC)
dorsiflexion- tibia moves anterior over planted foot
plantarflexion- tibia moves posterior over planted foot

31
Q

how much ROM in the ankle is needed for gait?

A

dorsiflexion- 10 deg

plantarflexion- 20 deg

32
Q

what is the ankle joint ROM?

A

dorsiflexion- 10 deg or more

plantarflexion- 45 deg or more

33
Q

what is happening to ankle joint during static stance?

A

Achilles pulls on calcaneus creating a plantarflexory moment to load the forefoot

34
Q

what is happening to ankle join tmotion during heel contact?

A

GRF posterior to ankle creates a plantarflexory moment
muscles anterior to ankle contract to reduce plantarflexion and decrease shock. Plantarflexion ends with forefoot loading.

35
Q

what is happening to ankle joitn motion during midstance.

A

fulcrum for GRF is at ankle.
tibia moves anteriorly on fixed foot
CKC dorsiflexion with internal rotation of leg

36
Q

what is happening to ankle joint motion during propulsion.

A

GRF anterior to ankle resulting in dorsiflexion.
heel pulled off ground by proximal structures.
knee flexion occurs to allow ankle to plantarflex and push off.
plantaflexion continues into swing phase

37
Q

what is happening to ankle joint motion during swing phase?

A

muscles dorsiflex the ankle to allow toes to clear ground

38
Q

which joints can compensate for ankle joint?

A
  1. knee
  2. MTJ oblique axis
  3. STJ
39
Q

what is tibial torsion?

A

external rotation

“a change in the axial relationship fo the foot to the thigh”

40
Q

intrauterine fetal position promotes what kind of rotation?

A

internal leg rotation

41
Q

at birth, what is the external malleolar position?

A

0-5 deg

42
Q

at one year, what is the external malleolar position?

A

10 deg

43
Q

how does the external malleolar position change as you age?

A

it increases by one degree for each year of age until 12 or 13 y/o

44
Q

what is the final result of external malleolar positioning?

A

18-23 deg

45
Q

but what is the actual amt of tibial torsion?

A

13-18 deg

46
Q

what is the most commonc ause of in-toe gait in children before the age of 2?

A

internal tibial torsion

47
Q

what is normal values of malleolar positioning?

A

18-23 deg

*lateral malleolus sits posteriorly

Biomechanics (14 decks)

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