Knee
Knee Extensor Mechanism (KEM) Quadriceps Patellofemoral Joint Quadriceps Tendon/Ligament Patella Tendon
Function of Patella
Mechanical Advantage rotary component of quadriceps force
Antatomy of Patella Facets Lateral Medial (7 mm) Odd (most media)
Antatomy of Patella
Patellofemoral Mechanics Knee Flexion Angle (degrees) Patella Contact 0 Little or no contact Inferior margin across medial & lateral facets Moves proximal and lateral Medial facet intercondylar notch, odd facet makes contact 135+ Contact via lateral and odd facets only
Patellofemoral Mechanics In general, With flexion, contact migrates from inferior to superior Medial facet receives most consistent contact Odd facet least
Patellofemoral Mechanics 25 knee flexion: 11 0 of medial tilting about a vertical axis (lateral lip) 7 0 of lateral rotation about an anterior- posterior axis
Patellofemoral Joint Reaction Forces Gait ( flexion) – 50% of BW Stair Climbing (60 0 of flexion) – 3.3 x BW Full Squat (135 0 ) – 7.8 x BW
Patellofemoral Joint Reaction Forces
Closed-Chain JRF increase from 0 – 90 0 flexion Open-Chain JRF decrease from 0 – 90 0 flexion
Patellofemoral Joint Reaction Forces Open-chain safest between 25 – 90 0 of flexion Closed-chain safest between of flexion
Meniscus – Vasucular Supply AgeMeniscus Region Birth – 12 months100% *18 months – 18 years 25 – 33 % 50+ 25%
Meniscus – Vasucular Supply
Meniscus – Neural Supply
Meniscus Innervation Inner 1/3 – none Outer 2/3 and horns (outer 1/3 > middle 1/3) Nocieptors (pain) Ruffini corpuscles (position) Pacinian corpuscles (acceleration) GTO (at end range)
Patella Rupture