Reporter: Chao-jung Hsieh Supervisor : Sai-wei Yang Date: 2007/5/10 The Influence of Vastus Muscle and Patella Alignment in Subjects With Patellofemoral Pain Reporter: Chao-jung Hsieh Supervisor : Sai-wei Yang Date: 2007/5/10

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

Pathomechanics Bony Alignment Soft Tissue Increased Q angle Patella malalignment Femoral anteversion Insufficient flexibility Strength deficit Abnormal biomechanics Abnormal patella tracking Excessive pressure on patellofemoral joint Patellofemoral pain syndrome

Literature review The EMG activity of the VMO is pronounced at the end-range of extension which emphasizes the function of the structure in providing medial patella stability Fulkerson 1990 Slow eccentric quadriceps open chain activity PFPS sufferers experienced a break in eccentric torque Anderson 2003

Purpose To investigate the influence of vastus muscle and patella alignment in subjects with PFPS Hypothesis Lateral patella tracking would be associated with Decreased vastus medialis oblique muscle fatigue rate and muscle activity relative to vastus lateralis The break phenomenon in eccentric torque curve and the level of pain

Methods Subjects: 30 subjects diagnosed with PFPS Preliminary examination: Postural alignment Leg length Femoral anteversion Tibial torsion Q angle Muscle flexibility test

Measured at 30°.45° and 60° of knee flexion Methods Condition: during muscle isokinetic contraction Variables: Patella alignment Lateral patella angle Lateral patella displacement Vastus medialis oblique and vastus lateralis Electrical activity (EA)-muscle activity Median frequency (MDF)-muscle fatigue Measured at 30°.45° and 60° of knee flexion

Methods Joint analysis of spectra and amplitude Slope of MDF Adaptation Force increase Slope of EA Force decrease Fatigue

Methods Equipments Electromyography Isokinetic dynamometer

Pilot study 1 female Age: 23 yrs BMI: 18.5 Right side Left side Leg length 87.5cm 87cm Femoral anteversion 9° 12° Tibial torsion 13° 16° Q angle 15° 18°

Lateral patella angle 13.7° 15.3° 17°

Patella lateral displacement Angle Ratio 30° 0.472024 45° 0.516143 60° 0.561106 Bisect offset method

Joint analysis of spectra and amplitude VL 120° VMO 60° VL 60° VMO 120°

Isokinetic knee flexion/extension 60° 120°

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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