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Winter 2023 - Essential Biomechanics and Kinesiology > Knee- WK10 ( Ch13) > Flashcards

Knee- WK10 ( Ch13) Flashcards

1
Q

Define normal genu valgus.

A

170-175 degrees of knee valgus due to angle of inclination of the femur

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2
Q

Define excessive genu valgus.

A

lateral angle less than 170 degrees

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3
Q

Define excessive genu varum.

A

lateral angle that exceeds about 180 degrees.

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4
Q

Name all the tissues that connect to the medial mensicus.

A

quadriceps and semimembranosus, MCL and medial capsule

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5
Q

Name all the tissues that connect to the lateral mensicus.

A

quadriceps and semimembranosus, popliteus, lateral capsule

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6
Q

Why can’t the menisci heal very well ?

A

Only outer 3rd is vascularized: the red zone

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7
Q

Which menisci is more frequently injured and why ?

A

medial meniscus due to a valgus force

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8
Q

Why would active hamstring strengthening after a fresh meniscal surgery potentially be detrimental to the tissue ?

A

semimembranosus attaches to both menisci and therefore would exert strain on either meniscus

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9
Q

How is knee rotation named ?

A

based on the position of the tibial tuberosity relative to the anterior distal femur.

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10
Q

What are the arthrokinematics of tibial on femoral knee extension and knee flexion.

A

extension: tibia anterior roll and slide
flexion: tibia posterior roll and slide

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11
Q

What are the arthrokinematics of femoral on tibial knee extension and flexion.

A

extension: femoral anterior roll and posterior slide; simultaneously
flexion: femoral posterior roll and anterior slide

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12
Q

What is the screw-home mechanism of the knee ?

A

ER of the knee to achieve full knee extension

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13
Q

What factors cause the screw-home mechanism ?

A
  1. shape of femoral condyles
  2. passive tension in ACL
  3. slight lateral pull of quadriceps
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14
Q

How does the knee get out of the screw home position ?

A

by internally rotating slightly; drive by popliteus

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15
Q

If the foot is planted and a valgus force is applied to the knee, what structures could be damaged ?

A

MCL, posterior medial capsule, ACL

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16
Q

What knee ROM makes the ACL most taut ?

A

As the knee approaches full extension

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17
Q

What affect does quad activation have on the ACL and in what ROM ?

A

quadriceps contraction stretches ACL increasingly taut as the knee approaches and reaches full extension

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18
Q

What knee ROM makes the PCL most taut ?

A

Like the ACL, most fibers are taut within most ranges of motion but the majority of the ligament is taut with flexion.

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19
Q

What affect does hamstring activation have on the PCL and in what ROM ?

A

hamstring contraction slides the tibia posteriorly becoming a PCL antagonist

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20
Q

What is the most common mechanism of injury for the PCL ?

A

falling onto a flexed knee w/ ankle plantar flexed
“dashboard injury”; tibia forced backwards by dashboard
associated with high energy trauma

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21
Q

How is the patellofemoral joint stabilized ?

A

by the quadriceps, articular fit, passive restraint from surrounding tissues

22
Q

How does the patella move durring knee flexion and extension ?

A

slides during DoP movement; fixed during PoD movement.

23
Q

When in the ROM does each part of the patella contact the trochlear groove ?

A

135 degrees of flexion: lateral facets and superior pole contacts femur below trochlear groove. See fig 13.23 pg. 557
90-60 degrees of flexion: patella engaged w/ trochlear groove
20-30 degrees: contact point is inferior pole of patella above the trochlear groove

24
Q

What structures make up the knee extensor mechanism ?

A

quadriceps, patellar tendon, and patella

25
Q

When in the ROM are external quad torques largest for: Open chain knee extension

A

0-45 degrees

26
Q

When in the ROM are external quad torques largest for: closed chain knee extension

A

45-90 degrees

27
Q

How would prescribe quad strengthening exercises for someone with patellofemoral joint pain ?

A

by optimizing when and where a load is applied therapeutically so as to not strain the extensors and thus the patella.

practically, allowing a patient to do the first 45 degrees of knee extension then allowing them to rise from a squat position

28
Q

During what ROM are internal quad torques present ?

A

45-70 degrees.

29
Q

How does the patella enhance quad function ?

A

functions as a spacer to increased the IMA of the quadriceps and the extensor mechanism

30
Q

Why does extensor lag occur ?

A

weak quadriceps, especially during the last 15-20 degrees of extension, cannot overcome the external flexor torques due to it’s increased leverage

31
Q

Why does PFJ compression increase with deeper squatting ?

A

by squatting deeper one increases the demand of the extensor mechanism; the QT and PT exert a combined compressive force on the PFJ.

32
Q

What are some local factors that could cause patellar mal-tracking in the trochlear groove?

A

lateral pull of quads, tension in IT band, flattened trochlear groove, patella alta, medial patellar retinacular fibers

33
Q

What are some global factors that could cause patellar mal-tracking in the trochlear groove?

A

excessive genu valgum, adduction of the femur ( hip); like with weakness of hip abductors

34
Q

When during knee ROM do hamstrings: have their best leverage and generate the most torque

A

(a) 50-90 degrees of knee flexion
(b) last 20 degrees of full extension

35
Q

why is the ROM for best knee leverage and ROM for torque generation different ?

A

knee flexion torque would be needed during maximal knee extension to flex the knee during walking or running

36
Q

Explain active and passive insufficiency for the quadriceps

A

active: hip flexed, knee extended
passive: hip extended, knee flexed

37
Q

Explain active and passive insufficiency for the hamstrings

A

active: hip extended, knee flexed
passive: hip flexed, knee extended

38
Q

What are some detrimental effects of: genu varum

A

medial unicompartmental OA ( see fig 13.35)

39
Q

What are some detrimental effects of: genu valgum

A

weakened MCL, PFJ tracking issues, OA

40
Q

What are some potential causes of genu valgum ?

A

weak abductors, previous injury, genetics, high BMI, ligament laxity

41
Q

What are some detrimental effects of: genu recurvatum

A

( hyperextension of the knee beyond 10 degrees )
continually weakened posterior structures

42
Q

What is Jumpers knee and why does it occur ?

A

chronic pain in patellar tendon

due to explosive, repetitive jumping sports, decreased dorsiflexion when landing, tendon oversue and wear

more stress placed on extensor mechanism

43
Q

What is patellofemoral pain syndrome (PFPS), what are its causes and how would you instruct someone to squat with this condition ?

A

-diffuse patellar pain w/ insidious offset
- neurologic, genetic, neuromuscular, or biomechanical causes
- to preferentially isolate hip extensors instead of quadriceps.

44
Q

What is the mechanism of injury for meniscal tears and what are the potential consequences of a partial menisectomy ?

A

mensicus injuries typically seen with forceful, axial rotation over fixed and planted knee

  • increased local stress, can cause wear and break down of articular cartilage
45
Q

What is the mechanism of injury for ACL injury ?

A

transient, forceful knee subluxation; like in sports

marked valgus collapse, strong quad activity, ER of the knee

46
Q

What is the terrible triad of the knee ?

A

ACL, medial meniscus, and MCL

47
Q

Why are female athletes more likely to tear an ACL than male athletes ?

A

greater valgus alignment when landing compared to males, stiff landings, reduced hamstring activation ratio to quads, see table 13.7

48
Q

How would you choose to strengthen the quads after an ACL surgery and why ?

A

squats
generally, exercises that require activation of hamstrings and quadriceps in preferentially flexed positions.

49
Q

What is the CPP and OPP of the knee ?

A

OPP: 25 degrees of flexion
CPP: full extension, and ER of tibia

50
Q

What are the ROM norms for flexion and extension for the knee?

A

flexion: 135 degrees
extension: 10 degrees

Winter 2023 - Essential Biomechanics and Kinesiology (16 decks)

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