The Knee Complex

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The Knee Complex
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The Knee Complex

• General Structure Function
• Structure Function of Specific Joints
• Muscular Considerations

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General Structure
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Joints of the Knee Complex
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General Function

• Provides very mobile link in an otherwise stable
  lower extremity
• Transmits loads from tibia/fibula to femur

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Knee Complex Movements
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• Transverse plane
• Medial and lateral
• rotation

• Sagittal plane
• Flexion, extension

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Knee Complex Movements

• Frontal plane
• Varus, valgus
• Anteroposterior translation
• Mediolateral translation

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The Knee Complex

1. General Structure Function
2. Structure Function of Specific Joints
3. Muscular Considerations

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Structure Function of Specific Joints

1. Tibiofibular Joint
2. Patellofemoral Joint
3. Tibiofemoral Joint

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Tibiofibular Joint Bony Structure
Amphiarthrodial membranous syndesmosis joint
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Structure Function of Specific Joints

1. Tibiofibular Joint
2. Patellofemoral Joint
3. Tibiofemoral Joint

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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

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Patella Structure

• Medial facet
• Lateral facet
• Odd facet (30)

M
L
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PF Articular Surfaces

• Largest sesamoid bone
• Least congruent joint
• Articular cartilage
• Vertical ridge
• Facets

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PF Articular Surfaces

• Largest sesamoid bone
• Least congruent joint
• Articular cartilage
• Vertical ridge
• Facets
• Angle of femoral sulcus

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Patellar Motion

• INF SUP Sliding
• Patellar tilt
• 11? MT as KN FL

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Patellar Motion

• Lateral rotation
• ACC MR of femur
• 6? through KN FL
• Medial rotation
• ACC LR of femur

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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

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Extension
Little effect overall
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Slight Flexion
Noticeable weakness
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Extreme Flexion
Noticeable weakness
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From 0 to 60 of Knee Flexion
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• 0?-60?
• Contact area ?
• ? MA of QF ? 60?
• ? ANT shear of QF

• 0?-60?
• Facet contact at 20?

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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

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During Full Extension

• Full EXT
• ? MA of QF
• ? QF length
• Patella very unstable

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PF JRF

• Amount of knee FL
• Strength of QF contraction

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PF Compressive Forces
Descending stairs 4000 N
Max isometric extension 6100 N
Kicking 6800 N
Parallel squat 14,900 N (7-8X BW)
Isokinetic knee extension 8300 N
Rising from chair 3800 N
Running/jogging 5000 N (3-4X BW)
Ascending stairs 1400 N
Walking 840-850 N (0.5-1.5X BW)
Cycling 880 N
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Compensatory Mechanisms for Compressive Force
Distribution

• Contact area ? with knee flexion
• Medial facet contact from 30?-70?
• Thickest hyaline cartilage in body

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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?

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Normal Patella Tracking

• Maintains maximum congruence
• Passive restraints
• Active restraints

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Abnormal Patella Tracking

• ? congruence
• Stretches capsule retinacula
• ? contact area

Lateral
Medial
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Causes of Abnormal Tracking

• Skeletal abnormalities
• Strength imbalance in QF
• Strength imbalance in fibrous tissues
• Compensatory movements in knee due to abnormal
  foot movement

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Causes of Abnormal Tracking

• Skeletal abnormalities
• Strength imbalance in QF
• Strength imbalance in fibrous tissues
• Compensatory movements in knee due to abnormal
  foot movement

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Skeletal Abnormalities Q-angle
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Skeletal Abnormalities Genu Varum Genu Valgum

• Q angle ? w/ age
• Varum common in very young children
• Valgum seen in growing children
• Menisectomy effects

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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

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Skeletal Abnormalities Patella Surface Lateral
Border

• Appositional forces ? in full extension
• Prominence of lateral border prevents lateral
  displacement
• Underdevelopment common in children as growing

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Skeletal Abnormalities Femoral Tibial Torsion

• Lateral tracking

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Causes of Abnormal Tracking

• Skeletal abnormalities
• Strength imbalance in QF
• Strength imbalance in fibrous tissues
• Compensatory movements in knee due to abnormal
  foot movement

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QF Strength Imbalance
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Causes of Abnormal Tracking

• Skeletal abnormalities
• Strength imbalance in QF
• Strength imbalance in fibrous tissues
• Compensatory movements in knee due to abnormal
  foot movement

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Fibrous Tissue Strength Imbalance
IT
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Causes of Abnormal Tracking

• Skeletal abnormalities
• Strength imbalance in QF
• Strength imbalance in fibrous tissues
• Compensatory movements in knee due to abnormal
  foot movement

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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

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Summary