knee part 2 Flashcards
what is tibiofemoral rotation at 90º flexion?
lateral 40º medial 30º via PROM
why is there more lateral rotation when the knee is flexed to 90º than medially?
there is more movement laterally because the AOR is further from the lateral compartment
where is the axis of rotation in the transverse plane at the tibiofemoral joint?
longitudinal axis that runs medial to the medial tibial intercondylar tubercle
what do the cruciate ligaments collectively check rein?
internal rotation because they are crossed
when are the cruciate ligaments slacked?
during external rotation when their unwinded from each other
during external rotation what ligaments are taut and are check reins?
the collateral ligaments
what plane do the femoral condyles lie in?
lateral in the sagittal plane
medial oblique to the sagittal plane
describe the lateral femoral condyle
> A-P dimension:
anterior projection buttress for patella to prevent lateral dislocations of patella
describe the medial femoral condyle
longitudinal dimension:
greater articulation surface for the tibia medially
what is the screw home mechanism?
an automatic, conjunct, obligatory ER of tibia with terminal 20-30º of knee extension
in OKC there’s an anterior roll and anterior slide, in the last 20-30º we run out of lateral anterior slide and continue medial anterior slide what is the result?
ER of tibia (leg)
in CKC as we stand up there’s and anterior roll and posterior slide, in the last 20-30º knee extension motion is stopped laterally but continued medially which results in what?
IR of femur = ER of tibia
how do the femoral condyles contribute to the screw home mechanism etiology?
there is greater SA more medial so there is more work to do on that side
how do the cruciate ligaments contribute to the screw home mechanism etiology?
the ligaments are tensioned and unwinding wanting to release tension which is ER rotation
what is the frontal plane posture at the tibiofemoral joint?
anatomic or longitudinal axis of the tibiofemoral joint is 5-10º of physiologic valgus.
stems from the femoral longitudinal axis being oblique that originates proximally from the proximal femoral angle of inclination
obliquity originates from the medial femoral condyle projecting farther distally than the lateral
what is the mechanical axis at the TF joint?
the weight bearing line from the center of femoral head to superior talus center (through the midline of the knee)
what results from an increase in valgus?
compression overload to the lateral TF compartment
distraction overload to medial TF compartment
what could occur over time due to genu valgus in the lateral compartment?
DJD, increased wear and tear, soft tissues on slack = adaptively shortened (IT band, LCL), lateral meniscus tear and patellar dislocation
what could occur over time due to genu valgus in the medial compartment?
soft tissue adaptively lengthen (MCL, gracilis, sartorius), capsule tension loaded, medial meniscus tear from pulling MCL, chondromalacia of joint, osteoclastic for bone
what results from a decrease in valgus?
compression overload to the medial TF compartment
distraction overload to lateral TF compartment
what could occur over time due to genu varus in the lateral compartment?
LCL, IT band, lateral compartment adaptive lengthening, decompressing lead to chondramalacia, osteoclastic activity of bone -> set up for hemiarthritic knee replacement
what could occur over time due to genu varus in the medial compartment?
DJD, medial meniscus tear, gracilis, sartorius, and MCL adaptively shorten
in frontal plane osteokinematics theres slight valgus with?
IR
in frontal plane osteokinematics theres slight varus with?
ER
what are frontal plane osteokinematics a result from?
9º posterior tibial slope
what affects the “length” of the medial or lateral compartments of the TF joint?
the position of the respective femoral condyle occupies on the tibial plateau
if the femoral condyle sits on the posterior plateau the compartment will be?
shorter
if the femoral condyle sits on the anterior plateau the compartment will be?
longer
what does sagittal plane motion create? why?
transverse plane motion. screwhome mechanism
what does transverse plane motion create?
frontal plane motion. screwhome mechanism
during external rotation what will the lateral femoral condyle do?
“climb up” the tibial slope, so lengthens the lateral compartment
during external rotation what will the medial femoral condyle do?
“fall down” the tibial slope, so shortens the medial compartment
if the leg is shorter medially what does this do?
pushes you into varus
explain 3 things that occur in external rotation
lengthened lateral compartment
shortened medial compartment
therefore produces TF varus
explain 3 things that occur in internal rotation
shortened lateral compartment
lengthened medial compartment
therefore produces TF valgus
are we gaining greater degrees of valgus or losing degrees of valgus as we extend our knee in OKC? explain your reasoning
lose valgus. at the end of knee extension we run out of room laterally and continue doing work medially (anterior slide). this causes ER of leg as the tibia moves on a relatively fixed femur (bringing the anterior portion of the tibial plateau backwards/posterior) which allows the lateral femoral condyle to sit on anterior portion of tibia on lateral compartment making us taller laterally. medially the tibial plateau is going anterior bringing more posterior aspect of tibial plateau in contact with medial femoral condyle which results in medial compartment shorter. when the medial compartment is shorter it drives the tibia/knee into varus gaining varus as we extend the knee to terminal extension. we lose valgus but still end up in 5-10º valgus
are we gaining greater degrees of valgus or losing degrees of valgus as we extend our knee in CKC? explain your reasoning
lose valgus. anterior roll posterior slide is occurring in a sit to stand. we run out of room laterally and have mor work to do medially so the femur IR the knee ER, the medial femoral condyle slides down the slope (posterior and shorter) lateral femoral condyle slides up the slope to anterior portion (taller). when we are longer laterally we are shorter medially which creates varus but 5-10º physical valgus
