Knee Flashcards
Knee is a _______ joint
____ DOF
Allows
modified hinge
2 DOF
Flex/Ext, ER/IR
Politeal Fossa Boundaries
Superolaterally: Biceps Femoris
Supermedially: Semitendinosus/Semimembranosus
Inferiorly: Gastroc
Popliteal Fossa Contents
tibial nerve
common fibular nerve
popliteal artery and vein
Tibiofemoral Joint Articulation
convex femoral condyles
concave tibial condyles and menisci
tibia on femur
concave on convex
Femur on tibia
convex on concave
Open pack position tibiofemoral
25 deg flexion
CPP Tibiofemoral
full extension, ER of tibia
Capsular pattern Tibiofemoral Joint
flexion more limited than extension
Knee Flexion End Feel
Tissue approximation (soft)
secondary to contact of muscle bulk of calf and thigh, or heel and buttocks
- Muscle tension or tightness of quads can result in a (end feel)
tissue stretch end feel
Knee Extension End Feel
Tissue stretch (aka “firm” or “capsular”) secondary to stretch of joint capsule and ligaments
Flexion ROM TF Joint
130-150
Hyperextension TF Joint
5-15 beyond 0
For Flexion/Extension M-L axis of rotation migrates (moves) within the
femoral condyles
TF Joint: Internal-External (Axial) Rotation increases with
knee in flexion
With knee flexed at 90, total motion for ER/IR is
40-45 deg
2:1 ER versus IR
Axial rotation of knee is based on the position of tibial tuberosity relative to
anterior distal femur
ER tibial tuberosity is
lateral to anterior femur
IR tibial tuberosity is
medial to anterior femur
Tibia can rotate internally or externally relative to a
stationary femur
Femur can rotate internally or externally relative to a
stationary tibia
Knee must be flexed to maximize independent ______ between the tibia and femur
axial rotation
Knee internal and External Rotation Involves a spin between the
menisci and the articular surfaces of the tibia and femur
The menisci are stabilized by
popliteus and semimembranosus muscles (have attachments to menisci)
To unlock fully extended knee in open chain kinematics —> the joint must first
internally rotate first
Unlocking the knee, action is driven by the
popliteus muscle (“the key to the knee” because it “unlocks” the knee)
Migration of the axis for flexion/extension during movement of the knee is known as the
evolute
Locking the knee in full extension requires
10 deg of tibial ER
Locking the knee tightens the
cruciates
Tibial-on-femoral knee extension (”open chain”): knee locks into extension as
tibia ER relative to a fixed femur
Femoral-on-tibial knee extension (“close chain”) knee locks into extension as
femur IR relative to a fixed tibia
“Screw Home” Mechanism of Extension
Shape of the medial femoral condyle curves about ___ degrees laterally as it approaches the ________
30
trochlear groove
“Screw Home” Mechanism of Extension
ACL tension helps pull
tibia into full extension
“Screw Home” Mechanism of Extension
Lateral line of pull of the
quadriceps
Proximal Tibiofibular Articulation
Proximal tibia (convex) and fibula (concave)
Distal Tibiofibular Articulation
Tibia (concave) and fibula (convex)
DF Osteokinematics
fibula moves proximally and slightly posteriorly away from the tibia
PF Osteokinematics
fibula moves distally and slightly anteriorly away from the tibia
Inversion Osteokinematics
fibula moves distally and slightly posteriorly
Eversion osteokinematics
fibula moves proximally and slightly anteriorly
