knee part 1 Flashcards
in the sagittal plane what is the tibialfemoral biomechanic morphology?
9º posterior tibial slope
femoral condyle decreasing radius of curvature
what functional requirements of flexion at the TF joint is needed for several tasks?
level surface gait: 60-68º
ascending stairs: 80º
descending stairs: 90º
sit-stand-sit transfers: 90º
tying a shoe: 106º
full squat to floor: 150-160º
what is the osteokinematic values for flexion at the TF joint in sagittal plane?
130-140º with hip flexion or 120º with hip extension
what is the osteokinematic values for extension at the TF joint in sagittal plane?
5-10º hyperextension
are the femoral condyles convex or concave?
convex
is the tibial plateau convex or concave?
concave
at the TF joint in OKC extension in sagittal plane what arthrokinematic motion is occurring?
concave tibial plateau moving on convex femoral condyles so tibial roll and slide occur in same direction (anterior)
during OKC extension at the Tf joint where do both the menisci translate and why?
anterior following the tibia because they are attached to the tibia and coronary ligaments
at the TF joint in OKC flexion in sagittal plane what arthrokinematic motion is occurring?
concave tibial plateau moving on convex femoral condyles so tibial roll and slide occur in the same direction (posterior)
the semimembranosis has an attachment where?
on the medial meniscus
the popliteus has an attachment where?
on the lateral meniscus
what are the functions of the menisci?
increase tibial plateaus radius of curvature
reduces TF friction
attenuates TF compression loads
at the TF joint in CKC flexion in sagittal plane what arthrokinematic motion is occurring?
convex moving on concave, posterior femoral roll followed by anterior femoral slide
by 15º of flexion in CKC what is occurring?
the medial compartment posterior roll begins to be accompanied by a small amount of anterior slide
why is knee flexion in CKC not initaited evenly upon compartments?
because there is greater SA on medial condyle for glide/slide articulation with medial tibial plateau than that of lateral femoral condyle and lateral tibial plateau. (essentially theres more work to do on medial side because more area to cover so has to start sooner)
what happens if only the medial compartment is sliding anterior?
creates external rotation of the femur which equals internal rotation of the knee
by 25º of flexion in CKC what is occurring?
lateral compartment roll begins to be accompanied by a small amount of anterior slide
what makes up the medial compartment?
medial femoral condyle and medial tibial plateau
what makes up the lateral compartment?
lateral femoral condyle and lateral tibial plateau
by mid ROM of flexion in CKC what is occurring?
approximately equal magnitude of posterior femoral roll and anterior femoral slide in both compartments
by late ROM of flexion in CKC what is occuring?
greater magnitude of anterior femoral slide than posterior femoral roll in both compartments
by end ROM of flexion in CKC what is occurring?
essentially all anterior femoral slide in both compartments
when is the angle of inclination greatest for the ACL?
at full extension
what is the rule for inert tissue (ligaments) in regards to angle of inclination?
when the angle of inclination is greatest for ligaments it puts the structure in a compromised position to do its job. more at risk for damage (tear)
what is the role of the ACL in closed chain?
to prevent posterior displacement of femur on fixed tibia
what is the roles of the ACL in open chain?
prevent anterior displacement of tibia on fixed femur
when does the ACL work best?
in flexion
what impact does hyperextension have on the ACL?
end ROM extension brings the midsubstance of ACL in contact with the femoral intercondylar shelf (notch of Grant). this contact point acts as a fulcrum to tension load the ACL
where does the ACL run?
antero-medial to postero-lateral
where does the ACL insert?
medial aspect of lateral femoral condyle
the anteromedial band of the ACL is taut when?
in greater degrees of flexion
the posterolateral band of the ACL is taut when?
in greater degrees of extension
the ACL has two bands what does this mean?
that some portion of the ACL is taut in all varying degrees of TF osteokinematic movement
the greatest excursion of tibia anteriorly at approx 30º which means what for the ACL?
neither bands are taut so this is where we do the lockmans test for ACL integrity
when is the angle of inclination greatest for the PCL?
at full flexion
when does the PCL work best?
in extension
where does the PCL project?
posteromedial to anterolateral
are there 2 bands of the PCL?
yes but they function the same so discussed together
where does the PCL insert?
medial aspect of lateral femoral condyle
