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What is the largest synovial joint?
Tibiofemoral
the T-F joint connects the two __________ lever arms in the body
longest
What are the two articulations of the T-F joint
Medial femoral condyle- medial tibial plateau and lateral femoral condyle- lateral tibial plateau
shape of femoral condyles in the frontal plane
slightly convex
shape of femoral condyles in the sagittal plane
convex
what attatches in the intercondylar fossa/notch
cruciate ligaments
what engages the patella during early flexion
trochlear groove
which tibial condyle has a greater anterior to posterior length?
medial
what fills the joint space on a radiograph
articular cartilage and meniscus
what is the function of the meniscus
increases contact area: stability, reduces friction, distributes forces evenly
What else contributes to stability (besides ACL)
meniscus
what is stress
force/contact area
which meniscus is more restricted and why? what does this mean in terms of injury
medial, connection to mcl, more prone to injury
when does swelling typically occur with a meniscal tear?
12-24 hours
which portion of the meniscus has good blood supply
red zone (outer 1/3)
which portion of the meniscus has poor blood supply
white zone (inner 2/3)
what arteries supply the meniscus?
genicular
why is immobilization/NWB problematic in meniscus injury
blood supply is aided by cyclic loading
functions of hyaline cartilage
decreases friction, distributes load, resists wear
how do focal lesions typically originate
trauma
what is normal alignment through the knee?
slight genu valgus (about 170-175 degrees)
Which sex typically has a wider angle of alignment of the T-F joint. Why?
males, males have a narrower pelvis than females
where the weight goes through the hip, knee, and ankle
Mechanical axes (LBA)
does the mechanical axes (LBA) change?
yes, with alignment
what is the normal frontal plane knee moment in bilateral stance?
none (no valgus/varus)
What is the static alignment of this knee?
genu varum
What is the static alignment of this knee?
genu valgum
what is the moment of this knee?
varus or ADDuction
what is the moment of this knee?
valgus or ABDuction
in knee ABD or ADD, what is it referring to?
the distal tibia
where in the knee would this person be prone to pain?
medial
where in the knee would this person be prone to pain?
lateral
which side of the knee is OA more prevalent? why?
medial, walking compresses the medial compartment
describe the GRF during single limb stance like during walking
GRF is medial, this pulls the knee into varus (ADDuction)
What is the axis of rotation in the knee?
horizontal line passing through the femoral epicondyles
the point of contact in the T-F joint is always directly beneath where the ___________ insert
cruciate ligaments
what mechanism keeps the femur on the tibia?
roll and slide
what is happening at the joint surface
arthrokinematics
What is the motion of the femur on the tibia during closed chain (weight bearing) flexion
rolls posteriorly and glibes anteriorly
What is the motion of the femur on the tibia during closed chain (weight bearing) extension
rolls anteriorly and glides posteriorly
What is the motion of the tibia on the femur during open chain (non-weight-bearing) flexion
roll and glide posteriorly
What is the motion of the tibia on the femur during open chain (non-weight-bearing) extension
roll and glide anteriorly
what knee ROM do most ADLs fall in?
1-100 degrees
is there greater available ROM of knee adduction/adduction in full extension or 20 degrees flexion
20 degrees flexion
does the knee have greater internal or external rotation?
external
what is the screw home mechanism during open chain?
external rotation of tibia on the femur during last 20 degrees of extension
what is the screw home mechanism during closed chain?
internal rotation of femur on the tibia during last 20 degrees of extension
3 factors guiding the screw home mechanism
longer medial femoral condyle (bony), ACL tension (ligament), lateral pull of quads (muscle)
what is unlocking the knee?
internal rotation of the tibia on the femur during early extension
what is the closed packed position in the knee
full extension
what is the loose packed position in the knee
about 25 degrees flexion
minimal bony congruence, lax ligaments, minimal intra articular pressure
loose packed position
maximum bony congruence and ligament taughtmness
closed packed position
4 main knee joint ligaments
ACL, PCL, MCL, LCL
what makes up the joint capsule?
retinaculum and synovial lining
how many bands do the ACL and PCL have
2
The acl is the primary restraint to ________ translation of the tibia on the femur and to ____________
anterior, hyperextension
secondary jobs of the ACL
contributes to frontal plane stability (resists IR and valgus/varus)
is the ACL more strained in flexion or extension? why?
extension, the patellar tendon has more angle which puts more anterior strain on the ACL
what reduces the stress on the ACL during squatting?
coactivation of hamstrings
why is PCL injured less than ACL
it is bigger and stronger
what is a good sign of PCL injury
abrasion on the tibial tubercle
when does the PCL act the greatest?
full flexion
what muscle would have loading restrictions early after a PCL injury?
hamstrings
primary role of PCL
restricts posterior translation of tibia on the femur
secondary role of PCL
frontal plane resistance
how many layers in the MCL?
3
which collateral ligament has a meniscal attachement
MCL
primary function MCL
resist valgus forces
primary function LCL
resist varus forces
what does the IT band have the same functions as?
LCL
function of posterior capsule
resists excessive hyperextension
variable and complex area with lots of little ligaments present including the LCL
posterolateral corner
During single limb stance how much weight does the medial compartment bear?
2.25 time body weight
During single limb strange how much weight does the lateral compartment bear?
.91 time body weight
Note
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