Transcript The Knee Complex

The Knee Complex
The Knee Complex
A. General Structure & Function
B. Structure & Function of Specific Joints
C. Muscular Considerations
General Structure
Joints of the Knee Complex
General Function
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Provides very mobile link in an otherwise
stable lower extremity
Transmits loads from tibia/fibula to femur
Knee Complex Movements
Sagittal plane
• Flexion, extension
Transverse plane
• Medial and lateral
rotation
Knee Complex Movements
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Frontal plane
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Varus, valgus
Anteroposterior translation
Mediolateral translation
The Knee Complex
A. General Structure & Function
B. Structure & Function of Specific Joints
C. Muscular Considerations
Structure & Function of
Specific Joints
1. Tibiofibular Joint
2. Patellofemoral Joint
3. Tibiofemoral Joint
Tibiofibular Joint:
Bony Structure
Amphiarthrodial membranous syndesmosis joint
Structure & Function of
Specific Joints
1. Tibiofibular Joint
2. Patellofemoral Joint
3. Tibiofemoral Joint
Purpose of Patella
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Increase leverage of QF
Protect joint during knee flexion
↓ pressure and distribute forces on femur
Prevent Fcompression on PT in resisted knee
flexion
Disadvantage:  ANT shear of QF
Patella Structure
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Medial facet
Lateral facet
Odd facet (30%)
M
L
PF Articular Surfaces
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Largest sesamoid bone
Least congruent joint
Articular cartilage
Vertical ridge
Facets
M
L
PF Articular Surfaces
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Largest sesamoid bone
Least congruent joint
Articular cartilage
Vertical ridge
Facets
Angle of femoral sulcus
Patellar Motion
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INF & SUP Sliding
Patellar tilt
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11 MT as KN FL
Lat
Med
Patellar Motion
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Lateral rotation
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ACC MR of femur
6 through KN FL
Medial rotation
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ACC LR of femur
Patellalectomy
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↓ MA of QF (↓ strength 49%)
 Q tendon friction
 compressive stress on groove by Q tendon
Most evident in closed chain EXT
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ECC QF in CC
Coupled w/ & assisted by hip & ankle movement
QF not needed in erect posture of CC
Extension
Little effect
overall
Slight Flexion
Noticeable weakness
Extreme Flexion
Noticeable weakness
From 0° to 60° of Knee Flexion
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0-60
Contact area 
 MA of QF;  60
 ANT shear of QF
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0-60
Facet contact at 20
From 60° to 140° of Knee
Flexion
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60-140
 contact area
 MA of QF
No leverage in full FL
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Overall
Medial facet most contact
Odd facet least contact
During Full Extension
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Full EXT
 MA of QF
 QF length
Patella very unstable
PF JRF
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Amount of knee FL
Strength of QF contraction
PF Compressive Forces
Descending stairs
Max isometric extension
Kicking
Parallel squat
Isokinetic knee extension
Rising from chair
Running/jogging
Ascending stairs
Walking
Cycling
4000 N
6100 N
6800 N
14,900 N (7-8X BW)
8300 N
3800 N
5000 N (3-4X BW)
1400 N
840-850 N (0.5-1.5X BW)
880 N
Compensatory Mechanisms for
Compressive Force Distribution
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Contact area  with knee flexion
Medial facet contact from 30-70
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Thickest hyaline cartilage in body
Compensatory Mechanisms for
Compressive Force Distribution
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Contact area  with knee flexion
Medial facet contact from 30-70
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Largest QF MA 30-70
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Thickest hyaline cartilage in body
QF torque as MA decreases
QF tendon contacts condyles 70-90
Normal Patella
Tracking
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Maintains maximum
congruence
Passive restraints
Active restraints
Abnormal Patella Tracking
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↓ congruence
Stretches capsule & retinacula
↓ contact area
Lateral
Medial
Causes of Abnormal Tracking
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Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Causes of Abnormal Tracking
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Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Skeletal Abnormalities:
Q-angle
Skeletal Abnormalities:
Genu Varum & Genu Valgum
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Q angle  w/ age
Varum common in
very young children
Valgum seen in
growing children
Menisectomy effects
Skeletal Abnormalities:
Patella Alta & Patella Baja
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Index of Insall & Salviti
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LT/LP
Normal = 1.0
Patella alta = 0.8
Patella baja = 1.2
Women  ratio
Skeletal Abnormalities:
Patella Surface Lateral Border
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Appositional forces ↓ in full
extension
Prominence of lateral
border prevents lateral
displacement
Underdevelopment
common in children as
growing
Skeletal Abnormalities:
Femoral & Tibial Torsion
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Lateral tracking
Causes of Abnormal Tracking
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Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
QF Strength Imbalance
Causes of Abnormal Tracking
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Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Fibrous Tissue Strength
Imbalance
IT
Causes of Abnormal Tracking
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Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Compensatory Movement
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Pronation of foot accompanied by medial rotation of
tibia  medial rotation & medial translation of patella
Pronation coupled w/ forceful quadriceps femoris
leads to anterior tilt
EX: jumping, landing, running
Summary