knee musculature - exam 2

Question 1

what muscles do knee flexion and internal rotation? what are their innervations?

Answer 1

sartorius - femoral n.
gracilis - obturator n
popliteus - tibial n
semimembranosus & tendinosus - sciatic n. (tibial portion)

Question 2

what muscle does knee extension & hip flexion? innervation?

Answer 2

quadriceps - femoral n

vastus group - 80% knee ext
rectus femoris - 20% hip flx, knee ext

Question 3

what muscles do knee flexion and ER? innervation?

Answer 3

biceps femoris (long head and short head) - sciatic n. (tibial and fibular portion)

Question 4

what muscles do knee flexion? innervation?

Answer 4

gastrocnemius
plantaris
both tibial n.

Question 5

what are isometric functions at the knee?

Answer 5

stabilizes to protect the knee

Question 6

what are eccentric functions at the knee?

Answer 6

like a spring
- controls the rate of descent of the body’s COM
- dampens impact/loading on the knee: walking - heel contact into loading knee flexion in response to GRF (controls knee flex)
- step down

Question 7

what are concentric functions at the knee?

Answer 7

accelerates tibia/femur toward extension
raises COG: jump, step up, stand up, running uphill

Question 8

the bigger the moment arm, the more _____ which = ______ level arm
Open chain?
Closed chain?

Answer 8

force
longer
Open chain: knee ext requires more torque
Closed chain: knee flex requires more torque

Question 9

is tibial on femoral extension open or closed chain?
femoral on tibial extension?
give an example of each

Answer 9

open chain (leg ext machine)
closed chain (squat)

Question 10

where is the largest moment arm/extension torque in 0 to 90 deg open chain? is this concentric or eccentric?

Answer 10

0 deg
concentric

Question 11

where is the largest moment arm/extension torque in 0-90 deg closed chain? is this concentric or eccentric?

Answer 11

90 deg
eccentric

Question 12

how do you minimize stress to the joint (aka the least amount of external torque applied) but still train the quads?

Answer 12

knee ext with weight 90-45 deg
partial sit to stand 0-45 deg

Question 13

what is extensor lag?

Answer 13

inability to complete full AROM tibial on femoral
knee can be fully extended passively
usually the last 15-20 degrees of ext

Question 14

extensor lag occurs where the _______ torque potential of the quads is the least and the _______ torque is the greatest

Answer 14

internal
external

Question 15

what is the functional role of the patella?

Answer 15

a spacer between femur and quads
increases the internal moment arm of the extensor mechanism
greatest between 20-60 deg

Question 16

What are the factors of PF alignment?

Answer 16

Quadriceps
Local Factors: act directly on the PF joint
Global factors: related to alignment of the bones/joints of LE

Question 17

Where do the quadriceps transmit the force when maintaining a partial squat?

Answer 17

quadriceps tendon and patellar tendon

QT & PT = an estimation of the PF joint compression force

Question 18

What are the factors that affect PF tracking: Quads

Answer 18

The larger the Q angle the greater the lateral mm. pull on the patella

—*Q angle or Quadriceps angle - is the overall line of force of the quadriceps, pull is lateral and posterior. The angle formed between the quads & patella tendon

Question 19

Which factors MOST likely resist excessive valgus or extremes of axial rotation of the TF jt. favor optimal PF tracking?

Answer 19

global factors (related to alignment of the bones/joints of LE

Question 20

Pt. slide w/ valgus unilateral stance. How can this happen?

Answer 20

laxity of/injury to MCL
adduction of femur (weakness hip aBd/tightness of aDd; compensated Trendlendburg - and GRF shift to lateral knee creating valgus torque
excessive pronation of ST jt. (IR of tibia)
reduced strength/neuro mm. control of ER of hip (IR of femur)

Question 21

Excessive genu valgum increases Q angle? T or F

Answer 21

True

Question 22

Screw Home Mechanism:
During the last 15-20º of knee extension with the FOOT FREE, the tibia rotates ____________and locks the knee into the extension

Answer 22

externally

Question 23

Screw Home Mechanism:
When the knee extends with the foot planted, the femur___________rotates and locks into the extension

Answer 23

internally

Question 24

The ________ unlocks the knee when walking, by ______ rotating the femur on the tibia during the ________ chain portion of the gait cycle

Answer 24

popliteus; laterally; closed chain

Question 25

In ________ chain movements popliteus muscle ________ rotates the tibia on the femur
—what movements (2)

Answer 25

open chain; medially
IR & Flexion

Question 26

What are the actions of the popliteus:

Answer 26

Knee Flexion (very minimal)
ER Femur (foot fixed)
IR Tibia (foot free)