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Chapter 6
The Knee
Introduction
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Little bony support
Tibiofemoral and patellofemoral joints rely
on soft tissue structures to control forces
transmitted through the joints
Femur and lower leg = body’s longest lever
arms
Clinical Anatomy
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Tibiofemoral joint – tibia, menisci, and femur
Patellofemoral joint must also function
properly
Bones & Bony Landmarks
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Figure 6-1, pg 186, Figure 6-2, pg 187
Femur
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Linea aspera
Medial and lateral condyles
Medial and lateral epicondyles
Clinical Anatomy
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Tibia
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Medial and lateral tibial plateaus
Tibial tuberosity
Patella
Fibular head
Proximal tibiofibular syndesmosis
Articulations and Ligamentous
Support
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Double condyloid articulation
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2 planes of motion: flexion/extension and
internal/external rotation
Accessory motions: valgus/varus and
anterior/posterior glide
Joint Capsule
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Figure 6-3, pg 187
Fibrous capsule surrounds circumference of knee jt
Medial, anterior, and lateral aspect
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Posterior aspect
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Capsule arises superior to femoral condyles and attaches
distal to tibial plateau
Capsule arises from the posterior margins of femoral
condyles above joint line and attaches to posterior tibial
condyle
Reinforcement from ligaments and muscles
Joint Capsule
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Synovial capsule lines articular portions of
fibrous joint capsule
Medially, anteriorly, and laterally
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Surrounds condyles of femur and tibia
Posteriorly
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Runs anteriorly along femur's intercondyler notch
and tibia’s intercondyler eminences, excluding the
cruciate ligaments
Collateral Ligaments
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Figures 6-4, pg 188
MCL - Primary medial stabilizer of knee
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Deep layer: thickening of joint capsule and
attaches to medial meniscus
Superficial layer: separated from deep layer by a
bursa, arises just below adductor tubercle and
inserts 7-10 cm below joint line
Protects knee against valgus stress
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Secondarily against external rotation of tibia and anterior
translation of tibia on femur, especially in absence of
intact ACL
Collateral Ligaments
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Figures 6-5, pg 188
LCL
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No attachment to meniscus or capsule
Arises from lateral femoral epicondyle and inserts
on proximal aspect of fibular head
Protects knee against varus stress when knee is
between full extension and 30o of flexion
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Secondarily against internal and external rotation of tibia
Cruciate Ligaments
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ACL
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Figures 6-6, pg 189
Arises from anteromedial intercondyler eminence
of tibia, travels posteriorly, passes lateral to PCL
and inserts on medial wall of lateral femoral
condyle
Stabilizes against:
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Anterior translation of tibia on femur, internal and
external rotation of tibia on femur, and hyperextension
of tibiofemoral joint
Cruciate Ligaments
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ACL has two segments that change positions
as the knee flexes, causing the ACL to wind
upon itself
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Anteromedial bundle
Posterolateral bundle
Figure 6-7, pg 189
Strain placed on ACL
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PROM vs. AROM vs. RROM
Cruciate Ligaments
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PCL
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Arises from posterior aspect of tibia and takes a
superior and anterior course, passing medially to
ACL, and attaches to lateral portion of femur’s
medial condyle
Stronger, wider than ACL; primary stabilizer of
knee
Provides restraint against:
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Posterior displacement of tibia on femur and external
tibial rotation
Cruciate Ligaments
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Posterior support also from popliteus
complex and posterior capsule
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Full extension – popliteus, posterior capsule, and
other joint structures
Midrange (40-120 degrees of flexion) –
anterolateral bundle of PCL
Beyond 120 degrees of flexion – posteromedial
bundle of PCL
Arcuate Ligament Complex
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Figure 6-9, page 190
Arcuate ligament complex
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Arcuate ligament, LCL, oblique popliteal ligament,
popliteus tendon, & lateral head of gastrocnemius
Provides support to posterolateral joint capsule
Assists in controlling posterolateral rotary
instability; injury to area results in increased
external rotation of tibia on femur
Proximal Tibiofibular Syndesmosis
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More stable than distal syndesmosis
Superior anterior and posterior Tibiofibular
ligaments
Anterior displacement is blocked by bony
outcrop of tibia
Fibular instabilities tend to occur posteriorly,
affecting peroneal nerve
The Menisci
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Fibrocartilaginous medial and lateral menisci
Menisci serve to:
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Deepen articulations of knee joint; increasing
load transmission over a greater percentage of
surface
Improve lubrication for articulating surfaces
Provide shock absorption
Increase stability of joint
The Menisci
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Figure 6-10, page 191
Wedged shaped, thick outer borders
Knee is more stable in weight bearing
Each menisci is divided into anterior, middle,
and posterior thirds
Vascular vs. avascular zones
Medial (C-shaped) vs., lateral (O-shaped)
The Menisci
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Coronary ligament
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Transverse ligament
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Joins anterior horns of each menisci
Patellomeniscal ligaments
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Attaches menisci at their peripheries to the tibia
Connects menisci to patella tendon
Ligament of Wrisberg and ligament of
Humphrey
The Menisci
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Knee extension
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Early flexion
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Patellomeniscal ligaments pull lateral meniscus
anteriorly, distorting its shape
Popliteus pulls lateral meniscus posteriorly
Later ROM
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Meniscofemoral ligament pulls posterior horn
medially and anteriorly
Muscles of the Knee
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Table 6-1, pages 192-193
Primarily serve to flex and extend
Anterior muscles
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Figure 6-11, page 191
Posterior muscles
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Figure 6-12, page 194
Popliteal fossa, figure 6-13, page 195
Muscles of the Knee
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Pes Anserine muscle group
Iliotibial Band
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Figure 6-14, page 195
The Screw Home Mechanism
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Unequal sizes of femoral condyles and the
tightening of the cruciate ligaments as they wind
upon themselves during flexion necessitates a
locking mechanism as the knee nears its final
degrees of extension