Lecture 61 - Biomechanics II Flashcards
What are the intracapsular vs extracapsular ligaments of the knee
Intra: ACL and PCL
Extracapsular = everything else
Function of meniscus
Shock absorber
Explain the arthrokinematics of the knee
Explain the screw home mechanism
Squatting, femur internally rotates on hip (closed chain)
Knee extension from flexion externally rotates tibia on femur (open chain)
Which sex is affected more by knee osteoarthritis and what is the physios role in OA
Females and physios role is to manage symptoms
What compartment of the knee is most impacted by osteoarthritis
Medial
What are some risk factors for osteoarthritis
What are 6 modifiable risk factors of osteoarthritis
What is a biomechanical risk factor of osteoarthritis and how can we reduce pain, delay or postpone knee arthroplasty
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
What is a persons COM/COG and what happens when we move
What are the 3 laws of newtons law of motion
What is the ground reaction force
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
What is the mechanical axis angle (MAA)
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)
- (-) MAA =
Varus and lcl stress
+ MAA =
Valgus and mcl stress
Explain knee adduction moment (KAM) - Dynamic
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
What does increased KAM-Dynamic cause
Creates tibial rotation in frontal plane in varus direction creating higher loads in medial knee compartment and increased osteoarthritis
How to treat KAM-Dynamics
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
What are the 3 types of clinical classifications for knee osteoarthritis and which one is most strict
Explain the 4 grades of kellgren-lawrence classification for OA
Magnitude of Ground Reaction Force (GRF) is determined by
the patient’s body mass and acceleration of the patient’s centre of mass (ie., Newton’s 2nd law: Force = mass x acceleration)
Off-Loading strategy to reduce KAM-Dynamic
-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
Affects of contralateral and ipsilateral cane on KAM
Affects of lateral wedge and shoe insert on KAM
They reduce pain but are not affective (clinically significant) for treating knee OA
Affects of stiffer shoes on KAM
Again, may reduce pain but are not clinically significant to treat knee OA
Affects of unloader brace on KAM and some disadvantages
-Reduce KAM and improve pain by transferring load away from medial compartment
Disadvantages: Bulky, irritating, costly resulting in noncompliance
Is quadricep strengthening important to reduce KAM and aid in knee OA
Yes
Is hip abductor strengthening important to reduce KAM and aid in knee OA
Yes
What is the best method to treat knee OA
Exercise
Describe Trendelenburg gait in terms of knee OA and KAM
Can gait modifications reduce KAM and aid in knee OA (and what’s something to be cautious about with modifying gait)
Yes
Can neuromuscular training reduce KAM and knee OA
Yes
Can manual therapy be used to treat OA
Very little support that it actually helps compared to exercise
Which pain killers are most and least effective at treating KAM and have the most adverse effects
Effects of visco on knee OA
Doesnt work and causes adverse effect
Effects of PRP ( Intra-articular treatments) on knee OA
Most effective injection but there is high risk of bias
Is a high tibial Osteotomy good at treating knee OA
Yes, and reduces likelihood or prolongs knee replacement
When is a knee replacement performed and what is the outcome
Explain the biomechanics of the patello-femoral joint
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%
The knee is a
Tricompartmental joint
Explain the affects of loading the patellofemoral joint
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)
What are some intervention strategies for patellofemoral pain and their grades of recommendation
What are some short and long term goals of knee OA
