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Biomechanics > Knee Biomechanics > Flashcards

Knee Biomechanics Flashcards

1
Q

femoral medial condyle & its effects

A

larger & slightly more inferior

- can effect standing posture & loading at the knee

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2
Q

sulcus angle

A

measured by the highest peaks of the medial and lateral femoral condyle to the deepest part of the trochlear groove

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3
Q

congruency angle

A

reflects patella position in the trochlear groove and the midpoint of the sulcus angle compared to the lowest portion of the patellar ridge

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4
Q

what does congruency angle inform you of?

A

if patella is prone to dislocation

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5
Q

distal femoral condyles

A

A/P convexity

M/L asymmetry

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6
Q

Tibia medial plateau plane

A

convex in all planes

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7
Q

Tibia lateral plateu planes

A

frontal - flat to slightly concave

sagittal - flat to slightly convex

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8
Q

fibula

A

primary association with ankle complex

-attachment site for LCL and bicep femoris

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9
Q

proximal tibial plateau

A
  • two shallow and concave surfaces

- medial section is deeper and has thicker cartilage

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10
Q

anterior capsule (supporting structures of knee)

A
  • quadriceps

- patellar retinacular fibers

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11
Q

lateral capsule (supporting structures of the knee)

A
  • lateral collateral ligament
  • lateral patellar retinacular fibers
  • iliotibial tract
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12
Q

medial capsule (supporting structures of the knee)

A
  • medial collateral ligament
  • medial patellar retinacular fibers
  • semimembranosus
  • pes anserinus
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13
Q

posterior capsule (supporting structures of the knee)

A
  • oblique popliteal ligamanent
  • arcuate ligament
  • popliteus
  • hamstring muscles
  • gastroc
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14
Q

posterolateral capsule (supporting structures of the knee)

A
  • arcuate ligament
  • lateral collateral ligament
  • popliteus muscle
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15
Q

Patella

A

generates force to move knee into extension

improve efficiency of movement through flexion

  • embedded w/in quadriceps tendon bridging quadricep vis quadricep tendon to the tibial tuberosity via patella tendon
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16
Q

menisci function

A
  • deepen joint to increase contact area & increase stability
  • acts as shock absorber & reduce friction

(fill in gap that would otherwise be present during movement)

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17
Q

meniscal ligaments

A
  • meniscotibial ligaments connect tibia and adjacent capsule to meniscus (loose & can pivot during movement(
  • transverse ligament connects menisci anteriorly
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18
Q

medial meniscus attachments

A

firmly attached to joint capsule

  • anchored to MCL
  • most commonly injured
  • allows for slight rotary motion
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19
Q

lateral meniscus attachments

A
  • nearly circular
  • smaller and more freely movable than medial meniscus
  • covers larger articular surface
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20
Q

load w/o meniscus

A

w/o menisci, compressive load increases by 3x

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21
Q

Q angle measurements

A

Line from ASIS to midpoint of patella & line from tibial tubercle

Normal

Male - 5-10 degrees
Femal - 10-15 degrees

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22
Q

Excessive Q angle

A

Genu Valgus

“knock-kneed gait”

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23
Q

Limited Q angle

A

Genu Varus

“bow-legged gait”

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24
Q

Normal Knee (tibia)

A

tibia almost vertical
femur has 5-10 degrees of varus

170-175 lateral angle

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25
Q

Tibial valgus

A

“knock knees” <165 (lateral)

“bow-legged” >180 (lateral)

26
Q

If you have increase valgus MCL will….

A

have more load because we are already in valgus / load lateral aspect of tibia more

27
Q

what might you expect with significant genu valgus?

A

more medial compressive stress

lateral tensile stress

28
Q

What does the “ascending” 1/3 of the lateral tibial plateau represent?

A

a location for fat pad impingement during knee joint hyperextension

(fat pads reduce friction)

29
Q

Tibiofemoral joint Flexion & Extension (sagittal plane)

A

ROM

-5-10 degrees of hyperextension to 130-140 degree of flexion

30
Q

Tibiofemoral joint Medial & Lateral Rotation (transverse plane)

A

40-50 degree of rotation (knee at 90 degree flexion)

2:1 ER to IR - full extension

31
Q

screw home mechanism

A

10 degrees external rotation (transverse plane) that occurs in full extension; twisting motion of the knee occurs during last 30 degree of extension (sagittal plane)

32
Q

screw home mechanism occurs due to

A
  • shape of medial femoral condyle
  • passive tension of the anterior cruciate ligament
  • lateral pull of quadriceps
33
Q

Patellofemoral joint (transverse plane view - inferior perspective)

A
  • 90 - 135
  • 60-90
  • 20-60

where the patella sits & follows a lateral facing “open C” track

34
Q

Medial Collateral Ligament

A
  • resist tibial valgus
  • carries valgus stress when knee is flexed
  • connected to medial meniscus
35
Q

Anterior Band of MCL

A

taut with flexion

36
Q

Posterior Band of MCL

A

taut with extension

37
Q

Lateral Collateral Ligament

A
  • no connections to capsule
  • resist adduction and tibial varus
  • limits lateral rotation of tibia
38
Q

ACL (anteromedial and posterolateral band)

A

anteromedial - 0-20 degrees primary resistance

posterolateral - 20-90 de resistance

39
Q

function of ACL

A

prevent forward displacement

  • carries 87% of load when anterior translational force is applied
  • taut in extension & relaxed in flexion
40
Q

PCL (anterolateral and posteromedial band)

A

anterolateral - 50-75% force between 40-120 degree of flexion

posteromedial band- 57% force beyond 120 degree of flexion

-taut during flexion

41
Q

function of PCL

A
  • prevents forward displacement of femur on tibia
  • carries 94% of load in extended knee when posteriorly-directed force applied to tibia

-taut during flexion

42
Q

Knee ROM depends on

A
  • hip positions due to biarticular muscles
  • interaction b/w calf and back of thigh limits flexion
  • joint mobility
  • pain
43
Q

open-packed position

A

25 degree of flexion

44
Q

close-packed position

A

full extension + ER

45
Q

Extension Arthrokinematics

“Fixed” Femur

A

convex - femur
concave - tibia

concave on convex - roll and slide in same direction

OPEN

46
Q

Extension Arthrokinematics

“Fixed” Shank

A

convex - femur
concave - tibia

convex on concave - roll & slide in opposite directions

CLOSED

47
Q

What happens during flexion (squat)

A
  • with rotation, femoral condyles roll of plateu ass they roll backward
  • prevent by sliding forward (ACL taut)
48
Q

the flexed position increases compressive stress due to

A

smaller contact area

49
Q

meniscectomy

A

taking tissue out (inner - less of healing compacity)

50
Q

meniscal repair

A

suturing tissue together (more vascularized -will heel)

51
Q

OATS (osteochondral autograft transfer system)

A

shave sites from non-weight bearing –> goes to lab and grow tissue and then put it back in

52
Q

Anterior Knee Joint muscles (torque)

A

quadricep

  • vastus lateralis
  • vastus medialis
  • vastus intermedius
  • rectus femoris

80% Torque = vastus
20% Torque = RF

53
Q

Posterior Knee Joint Muscles

A
  • Semimembranosus (medial)
  • Semitendinosus
  • Sartorius
  • Popliteus (lateral)
  • Bicep femoris
54
Q

additional function of bicep femoris

A

retract posterior horn of meniscus during knee flexion

55
Q

Lateral Knee joint muscles

A

bicep femoris

iliotibial band

56
Q

Load Progression (hardest to easiest)

A
  • single leg + external load
  • single leg squat
  • 2 down, one up
  • single leg assisted
  • staggered squat
  • body weight squat
57
Q

External torque =

A

body or leg weight X EMA

58
Q

Terminal knee extension

A

increased EMA x weight of shank = gradually increasing external torque

(more force)

59
Q

Squat

A

increased EMA x body weight = gradually decreasing external torque

(less force)

60
Q

PFJ compressive forces

A
  • deeper squat = requires greater force from the quadricep ( greater external torque on knee)
  • decreased angle of QT & PL produces greater joint force between patella and femur

Biomechanics (7 decks)

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