knee musculature - exam 2 Flashcards
what muscles do knee flexion and internal rotation? what are their innervations?
sartorius - femoral n.
gracilis - obturator n
popliteus - tibial n
semimembranosus & tendinosus - sciatic n. (tibial portion)
what muscle does knee extension & hip flexion? innervation?
quadriceps - femoral n
vastus group - 80% knee ext
rectus femoris - 20% hip flx, knee ext
what muscles do knee flexion and ER? innervation?
biceps femoris (long head and short head) - sciatic n. (tibial and fibular portion)
what muscles do knee flexion? innervation?
gastrocnemius
plantaris
both tibial n.
what are isometric functions at the knee?
stabilizes to protect the knee
what are eccentric functions at the knee?
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
what are concentric functions at the knee?
accelerates tibia/femur toward extension
raises COG: jump, step up, stand up, running uphill
the bigger the moment arm, the more _____ which = ______ level arm
Open chain?
Closed chain?
force
longer
Open chain: knee ext requires more torque
Closed chain: knee flex requires more torque
is tibial on femoral extension open or closed chain?
femoral on tibial extension?
give an example of each
open chain (leg ext machine)
closed chain (squat)
where is the largest moment arm/extension torque in 0 to 90 deg open chain? is this concentric or eccentric?
0 deg
concentric
where is the largest moment arm/extension torque in 0-90 deg closed chain? is this concentric or eccentric?
90 deg
eccentric
how do you minimize stress to the joint (aka the least amount of external torque applied) but still train the quads?
knee ext with weight 90-45 deg
partial sit to stand 0-45 deg
what is extensor lag?
inability to complete full AROM tibial on femoral
knee can be fully extended passively
usually the last 15-20 degrees of ext
extensor lag occurs where the _______ torque potential of the quads is the least and the _______ torque is the greatest
internal
external
what is the functional role of the patella?
a spacer between femur and quads
increases the internal moment arm of the extensor mechanism
greatest between 20-60 deg
What are the factors of PF alignment?
Quadriceps
Local Factors: act directly on the PF joint
Global factors: related to alignment of the bones/joints of LE
Where do the quadriceps transmit the force when maintaining a partial squat?
quadriceps tendon and patellar tendon
QT & PT = an estimation of the PF joint compression force
What are the factors that affect PF tracking: Quads
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
Which factors MOST likely resist excessive valgus or extremes of axial rotation of the TF jt. favor optimal PF tracking?
global factors (related to alignment of the bones/joints of LE
Pt. slide w/ valgus unilateral stance. How can this happen?
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)
Excessive genu valgum increases Q angle? T or F
True
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
externally
Screw Home Mechanism:
When the knee extends with the foot planted, the femur___________rotates and locks into the extension
internally
The ________ unlocks the knee when walking, by ______ rotating the femur on the tibia during the ________ chain portion of the gait cycle
popliteus; laterally; closed chain
In ________ chain movements popliteus muscle ________ rotates the tibia on the femur
—what movements (2)
open chain; medially
IR & Flexion
What are the actions of the popliteus:
Knee Flexion (very minimal)
ER Femur (foot fixed)
IR Tibia (foot free)