Transcript Non-Muscular-Anatomy-Handout-4x

Anatomy, Joint Orientation and
Arthrokinematics
Knee
Tibiofemoral Joint
• Femur run in a medial
and inferior oblique
direction
• Sits on a vertical tibia
Tibiofemoral Joint
• Femoral condyles are
convex
• Articular surface of
medial femoral and
tibial condyle larger
• Poor congruency
between the
articulating surfaces
Menisci
• Fibro cartilaginous disks
• Thicker peripherally
• Good blood supply
outer 1/3
• Rest Avascular
Menisci
• Roles within the knee
– Increase congruency
– Distribute weight
bearing across the knee
– Act as shock absorbers
– Aid lubrication reducing
friction
– Add nutrition to articular
cartilage
– Aid the locking
mechanism of the knee
Medial Menisci
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•
•
•
Larger than lateral
C Shaped
Larger posteriorly
Anchored to medial
capsule and MCL
• Anterior horn connects
with transverse ligament
• Lots of ligamentous and
capsular restraints
• Limits mobility increasing
injury risk
Lateral Menisci
• More Circular
• More Mobile
• Medial and lateral
meniscus move
posteriorly with flexion
• Medial and lateral
meniscus move anteriorly
with extension
• If a tear occurs, normal
movement is lost, causing
locking
Ligaments
• Coronary Ligament
– Part of the joint capsule
– Connect meniscu to
tibial plateau
– Often injured in twisting
injuries
Ligaments
• Transverse Ligament
– Connects the anterior
horns of the medial and
lateral menisci together
Ligaments
• Meniscofemoral
Ligament
– Posterior horn of lateral
menisci to medial
femoral condyle
– Anterior and Posterior
Divisions
Medial Collateral Ligament
• Strong flat ligament
• Merges with adductor
magnus fibres
• Deep portion attaches to
medial meniscus
• Deep portion capsular
thickening
• Seperated by pes anserinus
tendons by bursa
• Resists valgus force to the
knee and external rotation
of the tibia
Lateral Collateral Ligament
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•
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•
•
Cord like ligament
Extracapsular
More flexible than MCL
Resists varus stress
Resists tibial external
rotation
Anterior Cruciate Ligament
• Medial tibia to lateral
femoral condyle
• 2 bands
– Anteromedial
• Taut in knee flexion
– Posterolateral
• Taut in knee extension
• Resists anterior
translation of tibia on
femur and
hyperextension of knee
Anterior Cruciate Ligament
• Secondary restraint of
varus/valgus motion
• Prevents continued femoral
posterior translation during
closed chain flexion
• Intracapsular but
extrasynovial
• Blood vessels form a
periligamentous sheath
around the ligament
• Mechanoreceptors found in
femoral attachment
Posterior Cruciate Ligament
• Posterior intercondylar
area of tibia to medial
condyle of femur
• Twice as strong as ACL
• 2 Bands
– Anterolateral
– Posteromedial
• Merges with posterior
horn of lateral menisci
and meniscofemoral
ligament
Posterior Cruciate Ligament
• Restricts posterior
translation of tibia on
femur and external
rotation of tibia
• Secondary restraint of
varus/valgus motion
• Intracapsular, but
extrasynovial
Posterior Ligaments
• Oblique Popliteal Ligament
– Thickening of posterior
capsule
– Expansion of
semimembranosus tendon
– Passes superior and laterally
to femoral intercondylar line
• Arcuate Popliteal Ligament
– Inferior lateral aspect of
posterior capsule
– From fibula head to posterior
tibial and lateral femoral
condyle
Joint Capsule
• Thick ligamentous
sheath composed
mainly of muscle
tendons and their
expansions
• Deficient anteriorly due
to patella
Bursae
Infrapatella Fat Pad
• Sits between the joint
capsule and synovial
membrane
• Between Patella
Ligament and knee joint
• Can be impinged or
damaged in trauma
Arthrokinematics
Knee Extension
• Open Chain
– Tibia Glides Anteriorly and Rolls Anteriorly
– Tibia external rotation from 20° Flexion to Full Extension
• Closed Chain
– Femur Glides Posteriorly and Rolls Anteriorly
– Femur Internally rotates on stable Tibia from 20° Flexion to Full Extension
Knee Flexion
• Open Chain
– Tibia Glides Posteriorly and Rolls Posteriorly
– Tibia internal rotation from Full Extension to 20° Flexion
• Closed Chain
– Femur Glides Anteriorly and Rolls Posteriorly
– Femur Externally rotates on stable Tibia from Full Extension to 20° Flexion
Arthrokinematics
Extension
Flexion
Patellofemoral Joint
• Anterior surface of the
femoral condyles
• Posterior surface of the
patella
• Divided into medial and
lateral facets
• 4-5 mm of articular
hyaline cartilage on
patella
Ligamentum Patellae (Patellar Tendon)
• Continuation of
quadriceps tendon
• Attaches into the tibial
tuberosity
Meniscopatellar Fibres
• Fibrous bands running
from patella to lateral
aspect of medical and
lateral menisci
Retinaculum
• Medial and Lateral
• Expansions of different
connective tissue
• Patellofemoral and
patellotibial ligaments
• Vastus Medialis, Vastus
Lateralis, ITB
Patellofemoral Joint Arthrokinematics
• Articulation
– Inferior margin of patella articulates with the
femur at approx 10-20° of knee flexion
– As knee flexion increases the contact area of the
patella moves proximally
– As knee flexion increase the contact area of the
condyles moves posteriorly
– Patella does not articular with trochlea of femur
near terminal extension
Patellofemoral Articulations
Patellofemoral Articulations
Patellofemoral Contact Area
• The larger the contact
surface area the more a
load can be distributed
over a greater area
• E.g which is more
painful, a women
standing on you in
stilettoes or walking
boots?
• The contact surface of
the patellofemoral joint
INCREASES with flexion
• @ 30° knee flexion the
contact area = 2.0cm²
• @ 90 ° knee flexion the
contact area = 6.0cm²