Lec. 10: kin of knee Flashcards
Why is the knee jt considered a uniaxial MODIFIED hinge synovial joint
because you need external rotation of tibia to achieve last 10-15 degrees of TF joint extension
arthrokin at TF jt in CKC and OKC
CKC: roll and glide in opposite direction
OKC: roll and glide in same
CPP, Cap. pattern, and typical dislocation of TF jt
CPP: full EXT w/ EXT ROT of tibia
Cap. pattern: FLEX>EXT
typical dislocation: tibia moves POST or ANT (uncommon)
which lig limits valgus stress, EXT and LAT ROT and has inner fibers that blend with the MED meniscus and POST MED fibres that blend w/ the capsule
MCL
which lig limits varus stress, EXT and ER, is stronger than its counterpart, and doesn’t attach to the menisci or capsule
LCL
lig that limits EXT and varus stress on an extended knee, reinforces POST LAT jt, and has an aspect that passes over popliteus going towards fibular HD
arcuate popliteal lig
lig that prevents tibia from moving ANT on femur and limits hyperext, is supported by the hamstrings, and is intracapsular and extrasynovial
ACL
lig that limits EXT and valgus on an extended knee, reinforces POST MED jt, and is a tendinous expansion coming from semimembranosus
oblique popliteal
lig that prevents tibia from moving POST on femur, limits hyperflexion and hyperext and is the primary stabilizer at 90 degrees of knee FLEX, is supported by the quads, and is intracapsular and extrasynovial
PCL
ligs that holds menisci to tibial plateau
coronary ligs
lig that secures LAT meniscus to PCL and MED femoral condyle
meniscofemoral lig
lig that holds menisci to POST patella
patellomeniscal
lig that holds two menisci together
transverse lig
functions of MED and LAT meniscus (5)
- cushions impact
- distributes compressive force
- lubricates FLEX/EXT
- increases jt congruency
- limits ROT
what is O’Donahue’s triad
ACL, MCL, and MED meniscus are commonly injured together during excessive valgus stress to a flexed knee
why is the axis of rotation of the knee somewhat oblique
d/t the longer medial femoral condyle
why does the tibia lie slightly lateral to the femur in full EXT and slightly MED to the femur in full FLEX
b/c of the knees somewhat oblique axis
describe the tibial locking-unlocking mechanism
at terminal EXT the tibial intercondylar tubercles are lodged into the intercondylar notch by a “terminal rotation” or arthrokinematic spin
benefit of the locking/unlocking mechanism of the knee
when locked it provides stability so that the quads can relax
which mm is responsible for unlocking the femur and tibia
popliteus
which mms are responsible for locking the femur and tibia
tibia: biceps femoris and ITB
femur: adductor magnus
in full EXT in OKC the tibia is ___ ___
externally rotated
what degree angle is made at the knee from the anatomical axis of the femur and the anatomical axis of the tibia
obtuse angle of 185-190 opening medially
the normal ___ ___ ___ of the knee is important for allowing an equal distribution of force onto the femoral condyles
physiological valgus angle
the mechanical axis of the lower extremity passes through which 3 structures
hip, knee, and ankle
feats of genu varum (bow legged)
- angle is <175 degrees
- compressive force medially
- distraction force laterally
feats of genu valgum
- angle is >195 degrees
- compressive force laterally
- distraction force medially
another word for hyperextension of the knee in standing
genu recurvatum
CPP, cap. pattern, and typical dislocation of the patellofemoral jt
CPP: full FLEX
cap. pat: not really applicable, but the cartilage on the posteromedial patellar surface may see the greatest degeneration
typ. dislocation: superolateral
the PF jt changes its ___ during FLEX and EXT of the tibiofemoral jt to allow for optimal force development at the ___ ___
alignment, quadriceps femoris
what does the patella do in regards to force production
acts as an anatomical pulley which increases the moment arm and therefore improves torque production
the last 15 degrees of knee extension requires a ___% increase in quadriceps force b/c the moment arm is at its smallest
60
which patellar facet contacts the femur most consistently throughout knee FLEX
medial
in knee FLEX the forces applied to the patella by the quads tendon and the patellar tendon create a resultant force vector that does what
compresses the patella into the femur
at 10-15 degrees knee FLEX there is a joint reaction force on the patella of ~ ___x body weight. This increases to ~ ___-___x body weight at 130 degree
0.5, 7-8
if forces across the patella are improperly distributed what may happen
articular cartilage may begin to break down
intersection of a line from the ASIS to the midpoint of the patella, and another line from the center of the patella to the tib tube
Q angle
typical Q angle for men and women
men: 5-10
women: ~15 d/t wider pelvis
which mm group and mm support the ACL and pull the medial meniscus posteriorly during knee FLEX
hamstrings, semimembranosus
hamstrings are the most effective at flexing knee when hip is flexed b/c is prevents
active insufficiency of the hamstrings and passive insufficiency of rectus femoris
the hamstrings are ~ ___ as strong as the quads
2/3
___ and ___ are both active in hip flex and knee flex. Which one is most resistant against active insufficiency
sartorius and gracilis, sartorius
periostitis or MED tibial stress syndrome is also known as ___ ___ and is commonly caused by repeated ___ strain in runners who have tight calcaneal tendons or who hyperpronate
shin splints, soleus
in SLS the ___ helps balance the varus force of your weight which passes on the MED side of the knee
ITB
which mm is key in optimal patellar tracking
VMO
