Knee Biomechanics

Question 1

femoral medial condyle & its effects

Answer 1

larger & slightly more inferior

- can effect standing posture & loading at the knee

Question 2

sulcus angle

Answer 2

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

Question 3

congruency angle

Answer 3

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

Question 4

what does congruency angle inform you of?

Answer 4

if patella is prone to dislocation

Question 5

distal femoral condyles

Answer 5

A/P convexity

M/L asymmetry

Question 6

Tibia medial plateau plane

Answer 6

convex in all planes

Question 7

Tibia lateral plateu planes

Answer 7

frontal - flat to slightly concave

sagittal - flat to slightly convex

Question 8

fibula

Answer 8

primary association with ankle complex

-attachment site for LCL and bicep femoris

Question 9

proximal tibial plateau

Answer 9

• two shallow and concave surfaces

- medial section is deeper and has thicker cartilage

Question 10

anterior capsule (supporting structures of knee)

Answer 10

• quadriceps

- patellar retinacular fibers

Question 11

lateral capsule (supporting structures of the knee)

Answer 11

• lateral collateral ligament
• lateral patellar retinacular fibers
• iliotibial tract

Question 12

medial capsule (supporting structures of the knee)

Answer 12

• medial collateral ligament
• medial patellar retinacular fibers
• semimembranosus
• pes anserinus

Question 13

posterior capsule (supporting structures of the knee)

Answer 13

• oblique popliteal ligamanent
• arcuate ligament
• popliteus
• hamstring muscles
• gastroc

Question 14

posterolateral capsule (supporting structures of the knee)

Answer 14

• arcuate ligament
• lateral collateral ligament
• popliteus muscle

Question 15

Patella

Answer 15

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

Question 16

menisci function

Answer 16

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

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

Question 17

meniscal ligaments

Answer 17

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

Question 18

medial meniscus attachments

Answer 18

firmly attached to joint capsule

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

Question 19

lateral meniscus attachments

Answer 19

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

Question 20

load w/o meniscus

Answer 20

w/o menisci, compressive load increases by 3x

Question 21

Q angle measurements

Answer 21

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

Normal

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

Question 22

Excessive Q angle

Answer 22

Genu Valgus

“knock-kneed gait”

Question 23

Limited Q angle

Answer 23

Genu Varus

“bow-legged gait”

Question 24

Normal Knee (tibia)

Answer 24

tibia almost vertical
femur has 5-10 degrees of varus

170-175 lateral angle

Question 25

Tibial valgus

Answer 25

"knock knees" <165 (lateral) "bow-legged" >180 (lateral)

Question 26

If you have increase valgus MCL will....

Answer 26

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

Question 27

what might you expect with significant genu valgus?

Answer 27

more medial compressive stress | lateral tensile stress

Question 28

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

Answer 28

a location for fat pad impingement during knee joint hyperextension (fat pads reduce friction)

Question 29

Tibiofemoral joint Flexion & Extension (sagittal plane)

Answer 29

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

Question 30

Tibiofemoral joint Medial & Lateral Rotation (transverse plane)

Answer 30

40-50 degree of rotation (knee at 90 degree flexion) 2:1 ER to IR - full extension

Question 31

screw home mechanism

Answer 31

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)

Question 32

screw home mechanism occurs due to

Answer 32

- shape of medial femoral condyle - passive tension of the anterior cruciate ligament - lateral pull of quadriceps

Question 33

Patellofemoral joint (transverse plane view - inferior perspective)

Answer 33

- 90 - 135 - 60-90 - 20-60 where the patella sits & follows a lateral facing "open C" track

Question 34

Medial Collateral Ligament

Answer 34

- resist tibial valgus - carries valgus stress when knee is flexed - connected to medial meniscus

Question 35

Anterior Band of MCL

Answer 35

taut with flexion

Question 36

Posterior Band of MCL

Answer 36

taut with extension

Question 37

Lateral Collateral Ligament

Answer 37

- no connections to capsule - resist adduction and tibial varus - limits lateral rotation of tibia

Question 38

ACL (anteromedial and posterolateral band)

Answer 38

anteromedial - 0-20 degrees primary resistance posterolateral - 20-90 de resistance

Question 39

function of ACL

Answer 39

prevent forward displacement - carries 87% of load when anterior translational force is applied - taut in extension & relaxed in flexion

Question 40

PCL (anterolateral and posteromedial band)

Answer 40

anterolateral - 50-75% force between 40-120 degree of flexion posteromedial band- 57% force beyond 120 degree of flexion -taut during flexion

Question 41

function of PCL

Answer 41

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

Question 42

Knee ROM depends on

Answer 42

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

Question 43

open-packed position

Answer 43

25 degree of flexion

Question 44

close-packed position

Answer 44

full extension + ER

Question 45

Extension Arthrokinematics | "Fixed" Femur

Answer 45

convex - femur concave - tibia concave on convex - roll and slide in same direction OPEN

Question 46

Extension Arthrokinematics | "Fixed" Shank

Answer 46

convex - femur concave - tibia convex on concave - roll & slide in opposite directions CLOSED

Question 47

What happens during flexion (squat)

Answer 47

- with rotation, femoral condyles roll of plateu ass they roll backward - prevent by sliding forward (ACL taut)

Question 48

the flexed position increases compressive stress due to

Answer 48

smaller contact area

Question 49

meniscectomy

Answer 49

taking tissue out (inner - less of healing compacity)

Question 50

meniscal repair

Answer 50

suturing tissue together (more vascularized -will heel)

Question 51

OATS (osteochondral autograft transfer system)

Answer 51

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

Question 52

Anterior Knee Joint muscles (torque)

Answer 52

quadricep - vastus lateralis - vastus medialis - vastus intermedius - rectus femoris 80% Torque = vastus 20% Torque = RF

Question 53

Posterior Knee Joint Muscles

Answer 53

- Semimembranosus (medial) - Semitendinosus - Sartorius - Popliteus (lateral) - Bicep femoris

Question 54

additional function of bicep femoris

Answer 54

retract posterior horn of meniscus during knee flexion

Question 55

Lateral Knee joint muscles

Answer 55

bicep femoris | iliotibial band

Question 56

Load Progression (hardest to easiest)

Answer 56

- single leg + external load - single leg squat - 2 down, one up - single leg assisted - staggered squat - body weight squat

Question 57

External torque =

Answer 57

body or leg weight X EMA

Question 58

Terminal knee extension

Answer 58

increased EMA x weight of shank = gradually increasing external torque (more force)

Question 59

Squat

Answer 59

increased EMA x body weight = gradually decreasing external torque (less force)

Question 60

PFJ compressive forces

Answer 60

- 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