Unit 2 - Knee Flashcards
stability of the knee
ligaments, accessory structures, muscles that control varus/valgus, rotation
genu recurvatum
hyperextension >5 degrees
rotation of tibiofemoral joint
position dependent (greater in knee flexed, max at 90 deg flex) named by tibial tuberosity motion
coupled motion of the knee
sagittal and frontal plane, due to oblique orientation of axis
extension with valgus
flexion with varus
screw home mechanism
locking of knee in last 30 degrees of knee extension
lateral rotation of tibia on femur due to 3 factors:
1. lateral pull of quads
2. tension in ACL
3. shape of medial condyle
patellar motion with tf flexion
patella moves medially from a lateral position and glides inferiorly/rotates down intercondylar groove
patellar motion with tf extension
patella glides superiorly/rotates up and around condyles
arthrokinematics of tf extension
-taut pcl and anterior meniscus facilitates posterior glide of femur and anterior glide of tibia
arthrokinematics of tf flexion
taut ACL and posterior meniscus facilitate posterior glide of tibia and anterior glide of femur
semimembranosus (medially) and popliteus (laterally) pull on the meniscus which also facilitates posterior glide of tibia
arthrokinematics of tf rotation
about a longitudinal axis that tends to be on the medial tibial condyle
-distorts the meniscus
bundles of ACL and PCL
ACL: anteromedial and posterolateral
PCL: anterolateral and posteromedial
stressed at different knee angles
what resists anterior tibial translation
ACL posterior meniscus MCL ITB hamstrings gastroc and soleus in wb
what resists posterior tibial translation
PCL (is stressed most during 75-90 degrees of knee flexion) anterior meniscus quads popliteus gastroc
what resists valgus forces at the knee
MCL lateral meniscus ACL, PCL posterio-medial capsule semimembranosus tendon medial gastroc
what resists varus force at knee
LCL posterior lateral capsule and popliteus tendon ITB biceps femoris tendon medial meniscus ACL, PCL lateral gastroc
what resists medial rotation of the tibia
ACL, PCL
posterior-medial capsule
meniscus
biceps femoris
what resists lateral rotation of the tibia
posterior lateral capsule MCL, LCL popliteus sartorius/gracilis medial hamstrings meniscus
what resists genu recurvatum
ACL
posteromedial capsule/lig
posterolateral capsule/lig
how does the contact area of the patella change during tf movement
full extension: inferior pole
during flexion: moves inferiorly and medially
full flexion: lateral and odd facet only
laterally directed forces on the patella
ITB
bowstring force of the patella
lateral patellar retinacular fibers
overall line of quad force is slightly lateral
medially directed forces on the patella
medial patellar retinacular fibers
raised lateral facet of intercondylar groove
VMO
q- angle
angle of pull of the quads asis to midpoint of patella tibial tuberosity to midpoint of patella should be around 10-15 degrees increase in angle--increase in lateral force
what increases q-angle
structurally: femoral anteversion
lateral tibial torsion
valgus
dynamic: femoral medial rotation, tibial lateral rotation, valgus (as flexion occurs)
compression of pf joint
increases with increasing tf flexion angle (25-50% of bw while walking, 5-6x while running)
