The Knee Complex
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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
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
Frontal plane
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
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
Medial facet
Lateral facet
Odd facet (30%)
M
L
PF Articular Surfaces
Largest sesamoid bone
Least congruent joint
Articular cartilage
Vertical ridge
Facets
M
L
PF Articular Surfaces
Largest sesamoid bone
Least congruent joint
Articular cartilage
Vertical ridge
Facets
Angle of femoral sulcus
Patellar Motion
INF & SUP Sliding
Patellar tilt
11 MT as KN FL
Lat
Med
Patellar Motion
Lateral rotation
ACC MR of femur
6 through KN FL
Medial rotation
ACC LR of femur
Patellalectomy
↓ MA of QF (↓ strength 49%)
Q tendon friction
compressive stress on groove by Q tendon
Most evident in closed chain EXT
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
0-60
Contact area
MA of QF; 60
ANT shear of QF
0-60
Facet contact at 20
From 60° to 140° of Knee
Flexion
60-140
contact area
MA of QF
No leverage in full FL
Overall
Medial facet most contact
Odd facet least contact
During Full Extension
Full EXT
MA of QF
QF length
Patella very unstable
PF JRF
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
Contact area with knee flexion
Medial facet contact from 30-70
Thickest hyaline cartilage in body
Compensatory Mechanisms for
Compressive Force Distribution
Contact area with knee flexion
Medial facet contact from 30-70
Largest QF MA 30-70
Thickest hyaline cartilage in body
QF torque as MA decreases
QF tendon contacts condyles 70-90
Normal Patella
Tracking
Maintains maximum
congruence
Passive restraints
Active restraints
Abnormal Patella Tracking
↓ congruence
Stretches capsule & retinacula
↓ contact area
Lateral
Medial
Causes of Abnormal Tracking
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Causes of Abnormal Tracking
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
Q angle w/ age
Varum common in
very young children
Valgum seen in
growing children
Menisectomy effects
Skeletal Abnormalities:
Patella Alta & Patella Baja
Index of Insall & Salviti
LT/LP
Normal = 1.0
Patella alta = 0.8
Patella baja = 1.2
Women ratio
Skeletal Abnormalities:
Patella Surface Lateral Border
Appositional forces ↓ in full
extension
Prominence of lateral
border prevents lateral
displacement
Underdevelopment
common in children as
growing
Skeletal Abnormalities:
Femoral & Tibial Torsion
Lateral tracking
Causes of Abnormal Tracking
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
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
Skeletal abnormalities
Strength imbalance in QF
Strength imbalance in fibrous tissues
Compensatory movements in knee due to
abnormal foot movement
Compensatory Movement
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