Knee

Question 1

what kind of joint is the tibiofemoral

Answer 1

modified hinge

Question 2

on the femur, where does the lateral condyle lie

Answer 2

more directly in line with the shaft

Question 3

on the femur, where does the medial condyle lie

Answer 3

more distally

larger than the lateral condyle, impacts screw home mechanism

Question 4

on the tibia, what is the significance of the medial plateau

Answer 4

longer in AP direction

Question 5

on the tibia, what is the significance of the intercondylar eminence

Answer 5

ACC/PCL attach here

Question 6

tibiofemoral alignment

Answer 6

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)

Question 7

what does knee malalignment increase the likelihood of?

Answer 7

progressed OA

Question 8

which compartment of the knee accepts greater compressive forces with genu varum?

Answer 8

medial

Question 9

which compartment of the knee accepts greater compressive forces with genu valgum?

Answer 9

lateral

Question 10

what factors lead to genu valgum?

Answer 10

previous injury
genetic predisposition
high body mass index 
laxity of ligaments 
abnormal alignment & muscle weakness at either end of LE

Question 11

what are the results of genu valgum?

Answer 11

increase stress on MCL & lateral compartment
excessive lateral tracking of the patella
increased stress on ACL

Question 12

what can lead to genu varum?

Answer 12

thinning of articular cartilage on medial side

Question 13

what are the results of genu varum?

Answer 13

increased medial compartment loading
greater loss of medial joint space 
greater knee adduction movement 
increased strain on LCL
increased medial joint loading

Question 14

what can be used to offset unilateral compartmental OA?

Answer 14

an unloader brace

Question 15

what is high tibial osteotomy?

Answer 15

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

Question 16

how can genu recurvatum occur?

Answer 16

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)

Question 17

what is the Q angle? How is it formed? What is normal angle range?

Answer 17

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

Question 18

what happens if there is an increased Q angle?

Answer 18

increases lateral force on the patella –> lateral dislocation

Question 19

what local factors increase the lateral pull of the patella?

Answer 19

bowstringing force on the patella
tight IT band
excessive tension in lateral patellar retinacular fibers

Question 20

what local factors naturally oppose the lateral pull of the patella?

Answer 20

VMO
raised lateral facet of trochlear groove –> patella alta
medial patellar retinacular fibers

Question 21

what global factors increase the lateral pull of the patella?

Answer 21

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