EEI 10/17c Knee Biomechanics II Flashcards

1
Q

trochlear groove of the femur

A

where patella sits during extension

lateral side is larger and causes a buttress

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2
Q

Patellar anatomy

A
  1. Apex: patellar tendon
  2. Base: quad tendon
  3. Facets:
    - odd
    - medial
    - lateral
  4. Vertical Ridge
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3
Q

what is the significance of the patella?

A

wants to create balance and stay centered in the knee
BUT it is common for the patella to move laterally (because LCL is more mobile than MCL and lateral retinaculum pulls it because it’s stronger)

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4
Q

what is the retinaculum?

A

band of thickened deep fascia around tendons that holds them in place

-more dense on the lateral side

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5
Q

Q angle

A

angle from anterior superior illiac spine (ASIS) where sartorius attaches to the midline of the patella to the tibial tubercule

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6
Q

normal Q angles?

A

normal is 13-15 degrees

females have a greater Q angle and higher change of patellofemoral subluxations

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7
Q

why does the patella tend to move laterally?

A

Q angle is an anatomical feature that lends itself to move laterally

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8
Q

normal alignment

A
slight genu valgus
-angle from femur all the way down to the femur to tell valgus vs varus
normal: 170-175 degrees
varus >= 180 degrees (males more)
valgus <= 165 degrees (females more)
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9
Q

lower extremity valgus impact on patellofemoral joint

A

hip internal rotation and adduction
knee abduction
ankle/foot eversion and pronation
-has a lot to do with overuse problems

-DYNAMIC valgus!!

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10
Q

what are dynamic stabilizers against lateral translation?

A
  • Excessive knee external rotation causes patella translation laterally
  • Dynamic stabilizers against patella translation laterally
  • -Quad muscle!
  • -Rectus femorus (pulls more medially than laterally)

really important quad muscles for combating q angle and dynamic valgus that pulls knee cap laterally

  • -Vastis medialis (longis)
  • -Vastis medialis obliquis
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11
Q

what is the pennation angle?

A

pulls patella medially and helps to prevent lateral translation

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12
Q

static stabilizers against lateral translation

A

-lateral trochlea when knee cap and femur are in full extension
thickening of medial retinaculum

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13
Q

chronic patella dislocations

A

often because the patient is maintaining knee extension and patella is not sitting over the trochlea (it’s above it and not benefiting from the stability of the trochlea)

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14
Q

static stabilizers against medial translation

A
  • vastus lateralis (pennation angle that points laterally)

- lateral retinaculum: attached to IT band

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15
Q

proximal distal stabilizers for the patella

A
  • quad tendon (broad attachment to knee cap)

- patellar tendon coming down to the tibial tubercule

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16
Q

infrapatellar fat pad pathology

A

causes anterior knee pain
highly innervated
abnormal loads cause thickening of fat pad and will be a source of pain
-not a stabilizer!

17
Q

patella alta

A

high knee cap
-more common than patella baja
-when you take ratio of length of patella tendon to the length of the patella =1
if the ratio (insall salvatti index) > 1.2, knee cap is sitting higher
–> not engaging trochlea until 30-35 degrees of knee flexion

18
Q

patella baja

A

low knee cap ratio (insall salvatti index) < 0.8

19
Q

normal patellar kinematics

A

when you extend knee > patella moves proximal, anterior and extends
when you flex the knee > patella moves distally, posteriorly, and flexes

20
Q

when you want to improve patellar motion what do you do?

A

either superior (extension issue) or inferior (flexion issue) glides depending on the impairment

21
Q

medial/lateral manipulation of the knee cap

A
  • translation
  • tilting (lateral tilting when IT band is tight - naturally tilted more laterally)
  • rotation (does NOT happen often)
22
Q

as you move into flexion, what happens to the location of the patella?

A

closed chain: patella starts medial, moves lateral from 30-100 degrees, then moves medially in deep flexion > 100 degrees - odd facet articulates with the femur this is because of the medial patellofemoral ligament
open chain: quad force is tremendous in a full arc quad extension and the patella is above the femur in extension

23
Q

as you go deeper into knee flexion, what happens to the contact area of the patella and femur and what happens to the joint reaction force?

A

both increase!

24
Q

open chain vs closed chain joint reaction forces during flexion and extension

A
  1. Closed Chain:
    -Reduce joint reaction force by putting weight in hips and using glutes and quads instead of just relying on the knee and quads
    -Moment arm increases and the muscles have to work harder, contact area is high as you go into flexion
  2. Open chain:
    Quad force is tremendous in a full arc quad extension because moment arm is so long and contact area is small

Open chain has more stress even though the CA is smaller because the force of the muscle is tremendously larger

25
Q

patello femoral pain syndrome

A

not an acute anterior knee problem, caused by overuse

  • highly prevalent
  • multisport athletes are less likely to have this than single sport
  • can be because of local factors and distant factors (hyperpronation - distal; hip issues - proximal)
26
Q

significant drop in hips does what?

A

femur/hip into adduction and internal rotation

knee into valgus - BAD

27
Q

patellofemoral pain is associated with

A

peak hip ADDuction angle
peak internal rotation angle
contralateral hip drop

gait training reduces hip ADDuction angle

28
Q

effect of pronation on the knee

A

pronators show altered biomechanics of the foot - show eversion

alter biomechanics and knee and hip