The Knee Complex
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The Knee Complex
description
The Knee Complex. The Knee Complex. General Structure & Function Structure & Function of Specific Joints Muscular Considerations. General Structure. Joints of the Knee Complex. General Function. Provides very mobile link in an otherwise stable lower extremity - PowerPoint PPT Presentation
Transcript of The Knee Complex
The Knee Complex
The Knee Complex
A. General Structure & FunctionB. Structure & Function of Specific JointsC. 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 & FunctionB. Structure & Function of Specific JointsC. Muscular Considerations
Structure & Function of Specific Joints
1. Tibiofibular Joint2. Patellofemoral Joint 3. Tibiofemoral Joint
Tibiofibular Joint: Bony Structure
Amphiarthrodial membranous syndesmosis joint
Structure & Function of Specific Joints
1. Tibiofibular Joint2. 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%)
ML
PF Articular Surfaces Largest sesamoid bone Least congruent joint Articular cartilage Vertical ridge Facets
ML
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
MedLat
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
Little effect overall
Extension
Noticeable weakness
Slight Flexion
Noticeable weakness
Extreme Flexion
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 ForcesDescending stairs 4000 NMax isometric extension 6100 NKicking 6800 NParallel squat 14,900 N (7-8X BW)Isokinetic knee extension 8300 NRising from chair 3800 NRunning/jogging 5000 N (3-4X BW)Ascending stairs 1400 NWalking 840-850 N (0.5-1.5X BW)Cycling 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
Thickest hyaline cartilage in body Largest QF MA 30-70
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
