EEI 10/17c Knee Biomechanics II Flashcards
trochlear groove of the femur
where patella sits during extension
lateral side is larger and causes a buttress
Patellar anatomy
- Apex: patellar tendon
- Base: quad tendon
- Facets:
- odd
- medial
- lateral - Vertical Ridge
what is the significance of the patella?
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)
what is the retinaculum?
band of thickened deep fascia around tendons that holds them in place
-more dense on the lateral side
Q angle
angle from anterior superior illiac spine (ASIS) where sartorius attaches to the midline of the patella to the tibial tubercule
normal Q angles?
normal is 13-15 degrees
females have a greater Q angle and higher change of patellofemoral subluxations
why does the patella tend to move laterally?
Q angle is an anatomical feature that lends itself to move laterally
normal alignment
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)
lower extremity valgus impact on patellofemoral joint
hip internal rotation and adduction
knee abduction
ankle/foot eversion and pronation
-has a lot to do with overuse problems
-DYNAMIC valgus!!
what are dynamic stabilizers against lateral translation?
- 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
what is the pennation angle?
pulls patella medially and helps to prevent lateral translation
static stabilizers against lateral translation
-lateral trochlea when knee cap and femur are in full extension
thickening of medial retinaculum
chronic patella dislocations
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)
static stabilizers against medial translation
- vastus lateralis (pennation angle that points laterally)
- lateral retinaculum: attached to IT band
proximal distal stabilizers for the patella
- quad tendon (broad attachment to knee cap)
- patellar tendon coming down to the tibial tubercule