knee ligaments Flashcards
general functions of the ligaments
limit excessive knee extension
limit varus and valgus stresses
limit anterior and posterior translation of the tibia beneath the femur (also the femur on the tibia)
limits medial and lateral rotation of the tib on the femur
check rotary instabilities (combo of A-P translations and rotations –> stability in more than one direction)
ligaments in OKC
limit tibial motion
ligaments in CKC
limit femoral motion
medial collateral ligament (MCL)
runs from the medial femoral epicondyle
slopes anteriorly
inserts into the medial aspect of the proximal tibia
where does the MCL have attachments
joint capsule
medial meniscus
when is the MCL tight
full knee extension
primary function of MCL
resists valgus stress both in flexion and extension
contribution to valgus stability when flexed**
–> other structures in the knee have less contribution
will resist hyperextension of the knee
secondary fxns of MCL
will check lateral rotation of the tib
back up restraint to pure anterior displacement of tibia when ACL is absent
lateral collateral ligament (LCL)
runs from the lateral femoral epicondyle to the head of the fibula
where does the LCL have attachments
no where
when is the LCL tight
full knee extension
primary fxn of LCL
resist knee varus
secondary fxn LCL
resists medial rotation of the tibia
anterior cruciate ligament (ACL)
runs from the anterior tibia
between anterior insertions of the medial and lateral menisci
courses posteriorly, laterally and proximally across the knee joint
inserts on the medial aspect of the lateral femoral condyle
what happens as the ACL runs anterior to posterior
ACL turns outward in a slight spiral
how can the ACL be divided
anteromedial band
posterolateral band
anteromedial band of ACL
tightens with knee flexion
posterolateral band of ACL
tightens with knee extension
when can the ACL be torn
flexed or extended
where is the ACL
within the fibrous capsule but is extra synovial
outside the synovial layer –> not nourished by synovial fluid
primary fxn of ACL
resist anterior translation of the tibia on the femur
in knee joint flexion and extension
secondary fxn of the ACL
to limit tibial IR w/ knee in slight flexion
when all structures in the knee are in tact –> ACL plays a secondary role in preventing excessive tibial IR
–> IT band and lateral capsule are the primary restraints
what does the ACL have a small role in
resisting valgus and varus stress across the knee in the presence of deficiency of the collateral ligaments
when knee is in full extension
posterior cruciate ligament (PCL)
runs from its posterior tibial attachment superiorly and somewhat anteriorly to the inner aspect of the medial femoral condyle
how can the PCL be divided
anteromedial band
posterolateral band
anteromedial band of the PCL
maximally tight in 80-90 degrees of knee flexion
posterolateral band of the PCL
tight in extension
where is the PCL
within the fibrous capsule by extra synovial
PCL primary fxn
resist posterior displacement of the tibia on the femur
secondary fxn of PCL
resists tibial rotations
especially when the knee is flexed
what does the PCL play a small role in
resisting valgus and varus stressed across the knee
posterior capsule ligaments
oblique popliteal ligaments
arcuate ligament
both are tight in full knee extension and assist in preventing knee hyperextension
will resist valgus and varus stress when the knee is extended
oblique popliteal ligaments
runs from a point posterior to the medial tibial plateau to the central part of the joint capsule
arcuate ligament
y-shaped structure
attaches distally on the fibular and fans over the posterior capsule to joint the oblique popliteal ligament
joint capsule
has vertical fibers that are attached above the margins of the femoral condyles and the posterior margins of the tibial plateaus
is the joint capsule lax or tight
extensive structure that is fairly lax
allows a great amount of motion
how does the joint capsule extend
from the superior aspect of the quads tendon to the patellar ligament inferiorly
what is the joint capsule reinforced by
muscles and ligaments
extensor retinacula
the anteromedial and anterolateral portions of the capsule
also called the medial and lateral patella retinaculum
can affect patellar tracking
general form of the capsule
compares to a cylinder which is invaginated posteriorly
is the joint capsule innervated
highly innervated w/ mechanoreceptors
contributes to muscular stabilization of the knee joint by initiating reflex mediated muscular responses
synovial lining
most extensive and involved in the body
will follow the fibrous layer of the capsule except posteriorly where the synovium invaginates anteriorly
–> results in the ACL and PCL being within the fibrous capsule but not within the synovial lining
what will the synovial lining do during gestation
divide the knee into 3 compartments until 12 weeks of gestation
then the synovial septa are resorbed –> resulting in a sing joint cavity
plica
septa that are not completely resorbed and remain through adulthood
can be a cause of knee pain
when is the synovial lining most lax
when it has its greatest volume
approx 20-30 degrees of flexion
–> it can accommodate more fluid (has the greatest potential for fluid)
—-> contractures of the posterior muscles and structures
——–> keep knee extended after surgery
bursae
suprapatellar
prepatellar
superficial infrapatellar
deep infrapatellar
pes anserine
gastrocnemius
subpopliteus
suprapatellar
located b/w the femur and the quadriceps femoris muscle tendon
helps reduce friction b/w the two structures during knee extension
prepatellar
lies over the patella
fxns to cushion the anterior surface of the patella against direct trauma and reduce friction b/w the patella and the skin
superficial infrapatellar
lies b/w the patellar tendon and the skin
helps to reduce friction
deep infrapatellar
lies b/w the patellar ligament and the tibia
deep infrapatellar and superficial infrapatellar
facilitate gliding b/w those structures while we flex and extend the knee
reduce friction
pes anserine
lies b/w the proximal anterior medial aspect of the tibia and the undersurface of the pes anserine muscle tendons
“gooses foot”
gastrocnemius
lies b/w the medial femoral condyle and the medial gastroc tendon
subpopliteus
lies b/w the tendon of the popliteus and the lateral condyle of the tibia
infrapatellar fat pad
located at the anterior knee b/w the patellar tendon and the underlying synovial tissue and bone
acts as a cushion
highly innervated by nociceptors fibers –> irritation will cause pain
