1The tibiofemoral joint is a ________ synovial joint
bicondylar
2degrees of freedom in tibiofemoral joint
2 rotatory degrees, 1 in function
3con____ femoral condyles and con____ tibial plateau
vex
cave
4larger _______ condyle
medial
5tibial plateaus slope
posteriorly
6the femur angles in _______ correcting for a larger ______ condyle
medially
medial
7tibiofemoral is most stable in
full extension
max congruency between tibia and femur (intercondylar notch)
8What does tibiofemoral joint need to be functionally stable?
accessory structures (menisci)
joint capsule
ligaments
motor control (muscles which resist shear forces)
9in knee hyperextension what happens?
GRF passes anterior pushing the knee into extension
posterior ligaments are stretched
creep loading (strain), stiffness decreases which can lead to knee pain
10what happens in knee hypoextension (slightly flexed knee)?
exteneral moment into knee flexion (GRF posterior to knee joint axis)
quadriceps producing internal moment into knee extension
ligaments too slacked bc far from end range
compressive force increases (JRF)
11menisci increase the _______ of the tibial articulating surfaces
concavity
12menisci contribute to the distribution of ____ forces
weight bearing
increased surface Area -> decreased stress
13menisci act as ______ ______ to decrease load on articular cartilage
shock aborbers
14menisci are made of
fibrocartilage
resist compressive forces and some tensile forces
15menisci are thickest at the
periphery
thin centrally
16primary source of nutrition for menisci
synovial fluid through intermittent compressive loading
only the outer 1/3 is vascular
17what does menisci require to heal?
loading
compression sends signals to fibroblasts and osteoblasts
18menisci innervation
nociceptors and mechanoreceptors (proprioceptive function)
19medial meniscal attachments
tibia
patella
medial capsule
MCL
ACL
PCL
Semimembranosus
more likely injured!
20Lateral meniscal attachments
tibia
patella
acl
pcl
femur (meniscofemoral ligament)
popliteus
more malleable -> injury prevention
21close packed position of the knee
full extension
22loose packed position of the knee
25-30 degrees flexion
23joint capsule contains what joints?
both PFJ and tibiofemoral joints
24joint capsule innervated with
nociceptors and mechanoreceptors
252 layers of the joint capsule
superficial fibrous layer
deep synovial layer
26anterior portion of the fibrous layer spans
includes
length of the patella
extensor retinaculum - medial and lateral retinaculum
27posterior portion of the fibrous layer spans
reinforced by
femoral condyles to tibial condyles
arcuate ligament (lateral)
oblique popliteal ligament (medial)
28structures in the synovial layer
meniscus and cartilage
29intracapsular
everything inside of the fibrous capsule
30extrasynovial
inside the fibrous capsule but outside the synovial layer
ACL/PCL
Fat pads
31MCL superifical portion
medial epicondyle of femur to pes anserinus
32MCL deep portion
continuous with joint capsule
firmly attached to medial meniscus
33MCL nutrition source
direct blood supply
34Roles of the MCL
primary restraint to -
best in -
most important in -
genu valgum and tibial ER
full extension
slight flexion
35can the MCL resist anterior shear? ACL injury?
yes but does the best in extension - when it's not really needed
most work against knee valgus in slight flexion because other ligaments go slack
MCL injury puts more stress on ACL
36LCL attachments
lateral femoral condyle to fibular head
joins biceps femois at attachent
37is LCL continuous with joint capsule?
No, separate from the joint capsule
38LCL nutrition source?
Blood Supply
39LCL roles
reists -
best in -
most important in -
genu varum
full extension
slight knee flexion
40ACL attachments
proximal - posterior medial aspect of lateral femoral condyle
distal - lateral edge of medial tibial spine
412 bands of the ACL
anterior/medial
posterior/lateral
42ACL nutrition source
direct blood supply
43acl role
primary restraint to -
secondary roles of resisting -
anterior shear on tibia
frontal and transverse plane combinations
44easiest way to injury ACL
knee slightly flexed (loose pack position) and internally rotated
45ACL is slack in
slight flexion
46PCL role
primary restraint to -
best when the knee is -
secondary role resisting tibial -
posterior shear of the tibia
flexed
ER
47Impact of HS contraction when PCL is torn?
excessive posterior translation of the tibia
48as the femur rolls, how does the meniscus faciliate movement?
meniscus pushes back on the femur with equal and opposite force
some of that force is up, and some of the force in ant/post, which then helps it glide
49the meniscus is also ______
deformable
posterior during flexion
anterior during extension
50the acl helps with _____ glide of the femur during flexion
anterior
51the pcl helps with _____ glide of the femur during extension
posterior
52max rotation of the tibia available at
90 degrees of flexion
53tibial ________ needed for full knee extension, or femoral ________
external rotation
internal rotation
54role of knee flexors
knee flexion
internal/external rotation
55what muscles help the acl?
hamstrings
soleus
56what muscles go against the acl?
gastroc
57the quadriceps pull the patella in what direction?
superior and laterally
58the quadriceps produce a ______ force of the patella on the femur
compressive
59biggest predictor of amount of anterior shear of the tibia
position of the knee into flex/ext
greatest in slight flexion (10-30 deg)
60what degree of flexion is there no anterior shear
60-90 and after
61patella acts as an anatomical pulley to
increase MA of quads
62the peak MA of quadriceps and peak force occur between?
Impact on torque production?
45 and 60 deg of flexion
also where there is optimal length tension
match between mechanical advantage and ability to produce force
63because the patella is subject to high compressive forces, what should we find here?
cartilage
65patella has most amount of joint play in
full extension with relaxed quadriceps
66motion of the patella in knee flexion
inferior glide
medial rotation
medial glide
67motion of the patella in knee extension
superior glide
lateral rotation
lateral glide
68apex of the patella follows the
tibial tubercle
69frontal plane stability of patella at rest in extension
normal valgus angle
shallow superior sulcus
lateral line of pull from quads
70frontal plane stability of patella during flexion
increased stability as patella glides inferior deeper into sulcus
71longitudinal stabilizers of the patella
patella tendon
quad tendon
patellotibial ligaments
72transverse stabilizers of the patella
extensor retinaculum
MPFL
lateral lip of sulcus
muscle balance
73PFJ stress influced by
amount of active quadriceps force
angle of knee flexion - increased angle = increased passive quadriceps force
74pfj stress in open vs closed chain
open - stress increases from 90- 0
closed - stress increases 0-90 bc adding passive force
75how is the q angle related to PF stress
q angle used to predict what will happen to patella during contraction
a greater q angle = more pull from quadriceps = more stress BUT not risk factor for patellofemoral pain