Knee - Passive Structures Flashcards
what is the function of the meniscus?
distribute weight bearing forces
increase joint congruency
shock absorption
does the medial meniscus have greater or less mobility
less mobility due to greater ligamentous restraint
what are the connections to the medial meniscus
MCL, ACL, PCL and semimembranosus
what are the connections to the lateral meniscus
ACL, PCL, popliteus
where and when is the meniscus typically stressed?
at the posterior horn in the stance phase of walking
how does the meniscus deform in regards to compression?
deforms peripherally with compression which disperses stress
how is compression stress absorbed?
as circumferential tension –> hoop stress
a tear in the meniscus reduces ability to do what?
resist hoop stress
MOI of meniscus
axial rotation of condyles over flexed and weight bearing knee
how does the meniscus effect contact area and joint stress in the knee
increases contact area and reduces joint stress
what happens when there is a partial or complete tear
local stress is significantly increase on the meniscus and underlying articular cartilage
anterior cruciate ligament
primary restraint to anterior translation of tibia on femur
resists knee hyperextension, varus and valgus stresses, tibial rotation medially and laterally
posterior cruciate ligament
primary restraint to posterior translation of tibia on femur
resists varus and valgus stress, tibial rotation medially
medial collateral ligament
primary restraint to valgus force and lateral tibial rotation
also resists anterior translation of tibia on femur
lateral collateral ligament
primary restraint to varus stress
also resist tibial rotation laterally
iliotibial tract
assists ACL in resisting anterior translation of tibia on femur
what 3 factors are associated with non-contact injuries of the ACL
strong activation of quad over moderately flexed or nearly extended knee
marked valgus collapse of the knee
excessive ER of the knee
what position also is a common MOI for the ACL
excessive hyperextension with foot firmly planted
what is the MOI of the PCL
high-energy trauma – MVA or contact sports
falling onto fully flexed knee with ankle plantar flexed
dashboard injury
posterior sag sign **
