knee part 3

Question 1

what does the patella contribute to?

Answer 1

the quadriceps moment arm

Question 2

how much does the patella contribute to quadriceps MA when the knee is flexed to 90º?

Answer 2

13%

Question 3

how much does the patella contribute to quadriceps MA when the knee is fully extended?

Answer 3

31%

Question 4

if someone had a patellectomy what would this do?

Answer 4

no angle without patella and therefore no compressive resultant force

Question 5

what are the functions of the PF compressive force?

Answer 5

stabilizes patella in trochlea groove
patella assures “some” compression in full extension
patella not in femoral sulcus it is superior

Question 6

when is the patella more likely to dislocate or subluxation occur and why?

Answer 6

in extension because the patella is able to move more freely, in flexion the patella maintains more contact with the femoral sulcus

Question 7

what are the patellar contact areas and with how many degrees of flexion are they normally in contact?

Answer 7

the inferior 20º, middle 45º, superior 90º, lateral and medial (both 120º) poles of the patella.

Question 8

what is the normal ration for a normal length of patellar ligament to patellar height?

Answer 8

1:1

Question 9

what does patella baja mean?

Answer 9

the height of the patella is low riding, the height of the patella is longer than the patellar ligament

Question 10

what does patella alta mean?

Answer 10

the height of the patella is high riding, the height of the patella is smaller than the length of the patellar ligament

Question 11

what are some of the problems with patella baja?

Answer 11

it is going to take less degrees of flexion to contact the inferior pole of the patella which equals more time with inferior facets in contact which could lead to early onset degenerative changes. could be congenital or acquired (post ACL surgery).

Question 12

what could be considered a benefit of patella baja?

Answer 12

they spend more time in the sulcus which causes greater compression which inhibits or prevents a lateral or medial subluxation

Question 13

what are some of the problems with patella alta?

Answer 13

they spend more time out of the sulcus so they are more susceptible to dislocation. It takes greater degrees of flexion to contact. could get to 90º and maybe have only contacted the middle pole instead of the superior pole. Could require greater degrees of flexion to reach all poles. could lead to chondramalacia and or osteoblastic activity. it is congenital. it decreases the risk for degenerative.

Question 14

what does the patella do in terms at the tibial tuberosity?

Answer 14

acts as a link to focus the divergent pull of the 4 quads onto one single point at the tibial tuberosity

Question 15

how does the iliotibial band impact the patella?

Answer 15

the fascia slip from the IT band to the patella will add an additional force with the tendency to laterally translate the patella (sublux/dislocate)

Question 16

what are normal Q angles?

Answer 16

males 13º
females 18º

Question 17

what are the 3 landmarks for measuring the Q angle?

Answer 17

midpoint of the patella, straight line to the ASIS, down to the tibial tuberosity

Question 18

as the Q angle increase what else increases?

Answer 18

the odds the patella will track laterally (because set up to have lateral tracking of the patella)

Question 19

what are 3 things that can increase the Q angle?

Answer 19

laterally displace the tibial tubercle (external tibial rotation or external tibial torsion)
medially displace patella (internal femoral rotation, femoral anterversion)
laterally displace ASIS (females)

Question 20

when do we sublux the patella?

Answer 20

when we have the greatest Q angle
least P-F compressive force
greatest quad force (smallest quad MA, poor length tension relationship)
least patellar contact with femoral trochlea
full extension or hyperextension