Lecture 61 - Biomechanics II

Question 1

What are the intracapsular vs extracapsular ligaments of the knee

Answer 1

Intra: ACL and PCL
Extracapsular = everything else

Question 2

Function of meniscus

Answer 2

Shock absorber

Question 3

Explain the arthrokinematics of the knee

Answer 3

Question 4

Explain the screw home mechanism

Answer 4

Squatting, femur internally rotates on hip (closed chain)
Knee extension from flexion externally rotates tibia on femur (open chain)

Question 5

Which sex is affected more by knee osteoarthritis and what is the physios role in OA

Answer 5

Females and physios role is to manage symptoms

Question 6

What compartment of the knee is most impacted by osteoarthritis

Answer 6

Medial

Question 7

What are some risk factors for osteoarthritis

Answer 7

Question 8

What are 6 modifiable risk factors of osteoarthritis

Answer 8

Question 9

What is a biomechanical risk factor of osteoarthritis and how can we reduce pain, delay or postpone knee arthroplasty

Answer 9

Varus and valgus malalignments increase the medial and lateral stress distribution of the tibiofemoral
joint and have been associated with degenerative changes

Way to reduce: Shifting the axis with the greatest load away from the injured cartilage can reduce pain, delay or completely postpone knee arthroplasty

Question 10

What is a persons COM/COG and what happens when we move

Answer 10

Question 11

What are the 3 laws of newtons law of motion

Answer 11

Question 12

What is the ground reaction force

Answer 12

Equal and opposite reaction force exerted by ground on body during weightbearing activities (3rd law) and is determined by patients body mass and acceleration of their COM (2nd law)
** GRF combines both effects of gravity and movement/acceleration on body

Question 13

What is the mechanical axis angle (MAA)

Answer 13

Angle between mechanical axis of femur and mechanical axis of tibia (line from center of femoral head to center of femoral intercondylar notch that intersects and goes down tibial spine to talus)

Question 14

• (-) MAA =

Answer 14

Varus and lcl stress

Question 15

+ MAA =

Answer 15

Valgus and mcl stress

Question 16

Explain knee adduction moment (KAM) - Dynamic

Answer 16

Calculated as product of GRF generated by foot-ground interaction and perpendicular distance from knee center of rotation which is used to quantify effects of load reducing orthopedic interventions

Question 17

What does increased KAM-Dynamic cause

Answer 17

Creates tibial rotation in frontal plane in varus direction creating higher loads in medial knee compartment and increased osteoarthritis

Question 18

How to treat KAM-Dynamics

Answer 18

We need to understand these concepts and be able to offer conservative strategies for off loading based upon manipulating the ground reaction force and movement arm in the frontal plane

Question 19

What are the 3 types of clinical classifications for knee osteoarthritis and which one is most strict

Answer 19

Question 20

Explain the 4 grades of kellgren-lawrence classification for OA

Answer 20

Question 21

Magnitude of Ground Reaction Force (GRF) is determined by

Answer 21

the patient’s body mass and acceleration of the patient’s centre of mass (ie., Newton’s 2nd law: Force = mass x acceleration)

Question 22

Off-Loading strategy to reduce KAM-Dynamic

Answer 22

-limit the effect of the patient’s mass on the magnitude of the GRF (e.g., cane) or decrease the acceleration of the centre of mass (ie., reduce gait speed) may decrease the Knee Adduction Moment
- Maybe decrease length of the frontal plane KAM
lever arm

Question 23

Affects of contralateral and ipsilateral cane on KAM

Answer 23

Question 24

Affects of lateral wedge and shoe insert on KAM

Answer 24

They reduce pain but are not affective (clinically significant) for treating knee OA

Question 25

Affects of stiffer shoes on KAM

Answer 25

Again, may reduce pain but are not clinically significant to treat knee OA

Question 26

Affects of unloader brace on KAM and some disadvantages

Answer 26

-Reduce KAM and improve pain by transferring load away from medial compartment Disadvantages: Bulky, irritating, costly resulting in noncompliance

Question 27

Is quadricep strengthening important to reduce KAM and aid in knee OA

Answer 27

Yes

Question 28

Is hip abductor strengthening important to reduce KAM and aid in knee OA

Answer 28

Yes

Question 29

What is the best method to treat knee OA

Answer 29

Exercise

Question 30

Describe Trendelenburg gait in terms of knee OA and KAM

Answer 30

Question 31

Can gait modifications reduce KAM and aid in knee OA (and what's something to be cautious about with modifying gait)

Answer 31

Yes

Question 32

Can neuromuscular training reduce KAM and knee OA

Answer 32

Yes

Question 33

Can manual therapy be used to treat OA

Answer 33

Very little support that it actually helps compared to exercise

Question 34

Which pain killers are most and least effective at treating KAM and have the most adverse effects

Answer 34

Question 35

Effects of visco on knee OA

Answer 35

Doesnt work and causes adverse effect

Question 36

Effects of PRP ( Intra-articular treatments) on knee OA

Answer 36

Most effective injection but there is high risk of bias

Question 37

Is a high tibial Osteotomy good at treating knee OA

Answer 37

Yes, and reduces likelihood or prolongs knee replacement

Question 38

When is a knee replacement performed and what is the outcome

Answer 38

Question 39

Explain the biomechanics of the patello-femoral joint

Answer 39

The patellofemoral joint reaction force (red arrow) acts on the PF joint when knee is in high flexion (more knee flexed = more patella compression). Joint forces vary and depends on contraction of quads, extensibility of connective tissue, shape of patella and trochlear groove. Patella tries to increase mechanical advantage of quads mechanism increasing the force of knee extension by 30-50%

Question 40

The knee is a

Answer 40

Tricompartmental joint

Question 41

Explain the affects of loading the patellofemoral joint

Answer 41

1/3 of people over age 60 have patellofemoral OA and it is a significant source of pain and disability (same goes for tricompartmental OA)

Question 42

What are some intervention strategies for patellofemoral pain and their grades of recommendation

Answer 42

Question 43

What are some short and long term goals of knee OA

Answer 43