Flashcards in Knee Deck (110)
T/F: The knee is a bi-compartmental joint.
false, it's tri-compartmental
Knee joint stability is dependent on what?
passive restraint structural integrity (strength of ligaments)
How many planes of motion does the knee move through?
2: sagittal and horizontal planes
What does the longitudinal axis of LE tell you? What's a normal angle?
How straight up and down the leg is at the knee: 175 deg
- normally less than 180 since the angle of inclination makes the femur go in slightly (slight natural genu valgus)
With a mechanical axis of 150 deg, what does that tell you about the knee?
there's a genu valgus at the knee: axis is less than 175
What would a genu varus do to the longitudinal axis value?
make it >170
What degree classifies a genu recurvatum?
>10 degrees of hyperextension in the knee
What's an example of a secondary passive-restraint knee stabilizer?
Where is internal joint fluid pressure greatest in the knee?
at end ranges (is the least in slight flexion)
What is the position of comfort for the knee?
30 degrees flexion
What structures help make up the posterior capsule of the knee?
retinaculum comes from...
- vastus lateralis and medialis
- IT band
- popliteal oblique ligament
- arcuate oblique ligament
T/F: The tibiofemoral joint is inherently stable.
false- inherently unstable due to incongruent articular surfaces, leading to many knee injuries
What helps increase the articular congruency in the knee?
fibrocartilaginous menisci make tibial surface concave instead of flat; triples the tibiofemoral joint contact area
What do the medial and lateral menisci look like? What are they anchored by?
medial = lunar shape
lateral = C-shape
- anchored by the posterior horns
What is a tear of the posterior horns in the knee called? What can this lead to?
• bucket-handle tear, which is found in the inner-zone
• this can lead to unanchored menisci, = knee instability
If we didn't have menisci, how much larger would the compressive forces be on our body?
200x larger, causing bone degeneration (osteoarthritis)
What is the primary function of the menisci? What else does it do? (4)
primary = to reduce tibiofemoral joint compression
- also does proprioception, joint stabilization/congruency, arthrokinematic guidance, and articular cartilage lubrication
Why is it so bad to tear the inner zone meniscus?
b/c it's avascular and unlikely to heal; also nothing really anchoring menisci
Which is better, a peripheral tear or inner zone tear of the meniscus?
peripheral b/c it has a good blood supply
During what actions is the tibiofemoral joint most compressed?
• 4x compression during stairs
• 2.5-3x compression during walking
Weight bearing causes the menisci to wear down. Where does this occur?
on the periphery
What meniscus is more likely to tear? Why?
- medial is more likely to tear b/c it's attached to MCL and doesn't move as well
- LCL isn't attached to the lateral meniscus due to the popliteal ligament, so it's more moveable
How many degrees of freedom do we get at the tibiofemoral joint?
2: flex/extend and IR/ER
What ROM do we get for KE and KF?
KE = 0-10 degrees hyperextension, common in females
KF = 130-150 degrees
Why can we not get an exact measurement with a goniometer when measuring KE or KF? What landmark do we use to estimate?
- The ML axis of rotation migrates as we move through motion, following the condyle curves
- since the axis moves, this alters the moment arm of the muscles, so we have to just estimate the axis at the LATERAL EPICONDYLE
At what knee position do we get maximal IR and ER? Which do we get more of?
- when knee is flexed to 90 = max rotation
- get 2x more ER than IR (40-45 deg total)
What landmark do we use to measure rotation of the knee, and what's it relative to?
tibial tuberosity either pointing out or pointing in, relative to femur (foot will also be pointing either in or out usually)
Describe the arthrokinematics of open chain knee extension. What happens with the menisci during this?
tibia on femur = concave on convex
- rolls and slides anterior
- menisci are pulled anterior also via quads
Describe arthrokinematics of closed-chain knee extension.
femur on tibia = convex on concave
- roll anterior, slide posterior