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

Knee- WK10 ( Ch13) Flashcards

(50 cards)

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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 ?

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A

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

22
Q

How does the patella move durring knee flexion and extension ?

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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 ?

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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 ?

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A

quadriceps, patellar tendon, and patella

25
When in the ROM are external quad torques largest for: Open chain knee extension
0-45 degrees
26
When in the ROM are external quad torques largest for: closed chain knee extension
45-90 degrees
27
How would prescribe quad strengthening exercises for someone with patellofemoral joint pain ?
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
During what ROM are internal quad torques present ?
45-70 degrees.
29
How does the patella enhance quad function ?
functions as a spacer to increased the IMA of the quadriceps and the extensor mechanism
30
Why does extensor lag occur ?
weak quadriceps, especially during the last 15-20 degrees of extension, cannot overcome the external flexor torques due to it's increased leverage
31
Why does PFJ compression increase with deeper squatting ?
by squatting deeper one increases the demand of the extensor mechanism; the QT and PT exert a combined compressive force on the PFJ.
32
What are some local factors that could cause patellar mal-tracking in the trochlear groove?
lateral pull of quads, tension in IT band, flattened trochlear groove, patella alta, medial patellar retinacular fibers
33
What are some global factors that could cause patellar mal-tracking in the trochlear groove?
excessive genu valgum, adduction of the femur ( hip); like with weakness of hip abductors
34
When during knee ROM do hamstrings: have their best leverage and generate the most torque
(a) 50-90 degrees of knee flexion (b) last 20 degrees of full extension
35
why is the ROM for best knee leverage and ROM for torque generation different ?
knee flexion torque would be needed during maximal knee extension to flex the knee during walking or running
36
Explain active and passive insufficiency for the quadriceps
active: hip flexed, knee extended passive: hip extended, knee flexed
37
Explain active and passive insufficiency for the hamstrings
active: hip extended, knee flexed passive: hip flexed, knee extended
38
What are some detrimental effects of: genu varum
medial unicompartmental OA ( see fig 13.35)
39
What are some detrimental effects of: genu valgum
weakened MCL, PFJ tracking issues, OA
40
What are some potential causes of genu valgum ?
weak abductors, previous injury, genetics, high BMI, ligament laxity
41
What are some detrimental effects of: genu recurvatum
( hyperextension of the knee beyond 10 degrees ) continually weakened posterior structures
42
What is Jumpers knee and why does it occur ?
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
What is patellofemoral pain syndrome (PFPS), what are its causes and how would you instruct someone to squat with this condition ?
-diffuse patellar pain w/ insidious offset - neurologic, genetic, neuromuscular, or biomechanical causes - to preferentially isolate hip extensors instead of quadriceps.
44
What is the mechanism of injury for meniscal tears and what are the potential consequences of a partial menisectomy ?
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
What is the mechanism of injury for ACL injury ?
transient, forceful knee subluxation; like in sports marked valgus collapse, strong quad activity, ER of the knee
46
What is the terrible triad of the knee ?
ACL, medial meniscus, and MCL
47
Why are female athletes more likely to tear an ACL than male athletes ?
greater valgus alignment when landing compared to males, stiff landings, reduced hamstring activation ratio to quads, see table 13.7
48
How would you choose to strengthen the quads after an ACL surgery and why ?
squats generally, exercises that require activation of hamstrings and quadriceps in preferentially flexed positions.
49
What is the CPP and OPP of the knee ?
OPP: 25 degrees of flexion CPP: full extension, and ER of tibia
50
What are the ROM norms for flexion and extension for the knee?
flexion: 135 degrees extension: 10 degrees

Winter 2023 - Essential Biomechanics and Kinesiology (16 decks)

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