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The Influence of Vastus Muscle on Patella
Alignment and Balance in Subjects With
Patellofemoral Pain Syndrome
Reporter: Chao-jung Hsieh
Supervisor: Sai-wei Yang
Date: 2007/6/11
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Introduction
• Patellofemoral pain syndrome (PFPS)
Peripatellar or retropatellar pain results from physical
and biomechanical changes in the patellofemoral joint
Subjects with PFPS have more symptoms and pain
during the last 30° of maximal sitting knee extension
Thomee et al 1995
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Pathomechanics
Bony Alignment
Soft Tissue
Femoral
Patella
Increased
anteversion
malalignment
Q angle
Insufficient
flexibility
Strength
deficit
Abnormal biomechanics
Abnormal patella tracking
Excessive pressure on patellofemoral joint
Patellofemoral pain syndrome
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Literature review
• The EMG activity of the vastus medialis oblique is
pronounced at the end-range of extension which
emphasizes the function of the structure in providing
medial patella stability
Fulkerson 1990
• Effective control of balance also relies on a timely
response of strong muscles
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Purpose
• To investigate the influence of vastus muscle and
patella alignment in subjects with PFPS
• To evaluate the relationship of impairment of balance
and muscle strength of the knee
Hypothesis
• Vastus medialis oblique and vastus lateralis muscle
imbalance would be associated with
 Lateral patella tracking
 Poor balance
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Methods
• Subjects: 30 subjects diagnosed with PFPS
• Preliminary examination:
Postural alignment
Leg length
 Femoral anteversion
 Tibial torsion
 Q angle
 Muscle flexibility test

Estimating the pain intensity: visual-analog scale
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Methods
• Condition: during muscle isokinetic contraction
• Variables:
Patella alignment
Lateral patella angle
Lateral patella displacement
Measured at 30°.45° and
60° of knee flexion
Vastus medialis oblique and vastus lateralis
 Electrical activity (EA)-muscle activity
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Methods

Equipments
 Electromyography
 Isokinetic dynamometer
Stewart platform
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References
• Christopher MP(2000) Patellar kinematics, part I: The
influence of vastus muscle activity in subjects with and
without patellofemoral pain. Physical therapy. 10:956-964
• Davies AP, Bayer J(2004) The optimum knee flexion angle
for skyline radiography is thirty degrees. Clinical
orthopaedics and related research. 423:166-171
• Goran MH, Alwin L, Matthias J(2000) Methodologies for
evaluating electromyographic field data in ergonomics.
Journal of electromyography and kinesiology. 10:301-312
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Thanks for your listening
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