EEI 10/17c Knee Biomechanics II

Question 1

trochlear groove of the femur

Answer 1

where patella sits during extension

lateral side is larger and causes a buttress

Question 2

Patellar anatomy

Answer 2

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

Question 3

what is the significance of the patella?

Answer 3

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)

Question 4

what is the retinaculum?

Answer 4

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

-more dense on the lateral side

Question 5

Q angle

Answer 5

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

Question 6

normal Q angles?

Answer 6

normal is 13-15 degrees

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

Question 7

why does the patella tend to move laterally?

Answer 7

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

Question 8

normal alignment

Answer 8

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)

Question 9

lower extremity valgus impact on patellofemoral joint

Answer 9

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

-DYNAMIC valgus!!

Question 10

what are dynamic stabilizers against lateral translation?

Answer 10

• 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

Question 11

what is the pennation angle?

Answer 11

pulls patella medially and helps to prevent lateral translation

Question 12

static stabilizers against lateral translation

Answer 12

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

Question 13

chronic patella dislocations

Answer 13

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)

Question 14

static stabilizers against medial translation

Answer 14

• vastus lateralis (pennation angle that points laterally)

- lateral retinaculum: attached to IT band

Question 15

proximal distal stabilizers for the patella

Answer 15

• quad tendon (broad attachment to knee cap)

- patellar tendon coming down to the tibial tubercule

Question 16

infrapatellar fat pad pathology

Answer 16

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

Question 17

patella alta

Answer 17

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

Question 18

patella baja

Answer 18

low knee cap ratio (insall salvatti index) < 0.8

Question 19

normal patellar kinematics

Answer 19

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

Question 20

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

Answer 20

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

Question 21

medial/lateral manipulation of the knee cap

Answer 21

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

Question 22

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

Answer 22

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

Question 23

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?

Answer 23

both increase!

Question 24

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

Answer 24

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

Question 25

patello femoral pain syndrome

Answer 25

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)

Question 26

significant drop in hips does what?

Answer 26

femur/hip into adduction and internal rotation

knee into valgus - BAD

Question 27

patellofemoral pain is associated with

Answer 27

peak hip ADDuction angle
peak internal rotation angle
contralateral hip drop

gait training reduces hip ADDuction angle

Question 28

effect of pronation on the knee

Answer 28

pronators show altered biomechanics of the foot - show eversion

alter biomechanics and knee and hip