Knee Flashcards
what kind of joint is the tibiofemoral
modified hinge
on the femur, where does the lateral condyle lie
more directly in line with the shaft
on the femur, where does the medial condyle lie
more distally
larger than the lateral condyle, impacts screw home mechanism
on the tibia, what is the significance of the medial plateau
longer in AP direction
on the tibia, what is the significance of the intercondylar eminence
ACC/PCL attach here
tibiofemoral alignment
femoral shaft 170 to 175 laterally from tibial shaft
slight physiological valgus is normal
less than 165 degrees: excessive genu vlagum (knock knees)
greater than 180 degrees: genu varum (bow legs)
what does knee malalignment increase the likelihood of?
progressed OA
which compartment of the knee accepts greater compressive forces with genu varum?
medial
which compartment of the knee accepts greater compressive forces with genu valgum?
lateral
what factors lead to genu valgum?
previous injury genetic predisposition high body mass index laxity of ligaments abnormal alignment & muscle weakness at either end of LE
what are the results of genu valgum?
increase stress on MCL & lateral compartment
excessive lateral tracking of the patella
increased stress on ACL
what can lead to genu varum?
thinning of articular cartilage on medial side
what are the results of genu varum?
increased medial compartment loading greater loss of medial joint space greater knee adduction movement increased strain on LCL increased medial joint loading
what can be used to offset unilateral compartmental OA?
an unloader brace
what is high tibial osteotomy?
done when there is unilateral severe knee OA
cuts out a wedge of bone in the lateral tibia to reduce severity of varus alignment, allowing the lateral side to bear more weight
how can genu recurvatum occur?
secondary to laxity of posterior capsule and knee flexors
occur due to overpowering knee extension torque – secondary to poor postural control or neuromuscular disease (spasticity/paralysis)
what is the Q angle? How is it formed? What is normal angle range?
estimation of the line of pull of quadriceps
formed between line connecting ASIS to middle of patella and line connecting tibial tuberosity to middle of patella
normal range: 13-15 degrees
what happens if there is an increased Q angle?
increases lateral force on the patella –> lateral dislocation
what local factors increase the lateral pull of the patella?
bowstringing force on the patella
tight IT band
excessive tension in lateral patellar retinacular fibers
what local factors naturally oppose the lateral pull of the patella?
VMO
raised lateral facet of trochlear groove –> patella alta
medial patellar retinacular fibers
what global factors increase the lateral pull of the patella?
Excessive Genu valgum increases Q-angle and lateral bowstringing force, ER of the knee increase Q-angle
Excessive pronation (eversion) of subtalar joint also can create excessive valgus load
Excessive IR of knee while walking
Compensated Trendelenburg sign shifts ground reaction force lateral to stance and increases knee valgus
