Overview of the Knee/Patho/Stabilizers Flashcards
What are the three joints that make up the knee joint complex?
tibiofemoral
-type: bicondylar- hinge
-articulation: lateral and medial condyles of the femur with the tibial plateaus
patellofemoral
-type: plane/gliding
-articulation: trochlear groove of the femur with the posterior surface of the patella
proximal tibiofibular
-type: plane/gliding
-articulation: fibular head with the lateral tibial condyle
The function of the femoral condyle morphology/screw-home mechanism
Provides increased stability to the knee through bony congruency AND ligamentous tension
the tibia externally rotates as the knee reaches full extension due to the increased size of the medial femoral condyle compared to the lateral femoral condyle
The screw home mechanism from 30 degrees to 0 degrees
the tibia externally rotates as the knee reaches full extension
provides increased stability to the knee
DUE TO :
-the shape of the medial femoral condyle
-lateral pull of quadriceps
-tension in ACL
LCL reconstruction restraints
-no resisted knee flexion due to attachment of hamstrings on the fibular head
-no ER
-no hyperextension (positioned posterior to the knee joint)
-no varus forces
MCL precautions after reconstruction
-no resisted knee flexion
-capsule attaches to the deep layer of th eMCL
The function of menisci and blood supply:
absorb shock, decrease friction, increase the contact area
-designed to distribute forces outward
BLOOD SUPPLY OF MENISCI:
-the meniscus is composed of fibrocartilage
-the blood flow is greatest in the peripheral one-third and is least in the central one-third
-healing capacity is vascularity and age-dependent–> can end up with degenerative tears
Meniscus repair
-lesion has to be in the vascular zone
-have to have intact peripheral circumferential fiber and minimal damage to the meniscus body
-lesion must be longer than 8 mm
MEDIAL MENISCUS REPAIR:
-Femoral condyle
imparts a sheer force
to meniscus in
weight bearing
beyond 115-120
degrees of knee
flexion
-Hamstring
Contraction
indirectly “tugs” on
posterior horn of
meniscus–> reduce stress by preventing activation of hamstrings too early
Patellofemoral joint characteristics
type: plane/gliding
-posterior surface of the patella is covered with thick hyaline cartilage
PATELLA:
-bottom: apex (attachment of patellar ligament)
-posterior aspect has a medial facet and lateral facet and odd facet
-lateral facet is broader than medial facet
odd facet in full flexion
At full flexion, the odd facet is the only articulating contact between the patella and the lateral surface of medial femoral condyle.
What is the function of the trochlear groove in the PFJ?
depth of the groove provides stability
TROCHLEAR DYSPLASIA:
-a shallow trochlear groove
-can increase the likelihood of patellar dislocation
When do compressive forces increase at the PFJ?
increase with greater knee flexion
increase with quadriceps muscle force production
*surface area of contact increases with flexion–> increased surface area results in reduced focal areas of pressure
–> this would not be as beneficial in pt with reduced hyaline cartilage
Arthrokinematics of patella in trochlear groove
flexion- inferior glide
extension- superior glide
-medial and lateral gliding as it traverses through the groove
Soft tissue restraints of the patella
medial and lateral retinaculum
medial patellofemoral ligament - thickening of the medial retinaculum —> a graft repair of this ligament can be very effective and strong
What are some anatomical factors for patellar instability?
-MPFL or retinacular deficiency
-shallow trochlear groove
-flat patella
-patella alta
Arthrokinematics of the PTFJ
knee extension: joint glides posterior
knee flexion: joint glides anterior
