Weight-training exercise increased knee muscle strength and the patellofemoral joint contact area, which could reduce mechanical stress in the joint, improving pain and function in subjects with PFPS.

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Context: Underconditioned patellar stabilizing muscles could be a predisposing factor for patellar instability.Objective: To examine the effect of 2 modes of weight training on the size of the vastus medialis obliquus (VMO), the resting position and passive mobility of the patella, and the strength of the knee extensor muscles.Design: Prospective intervention, repeated measures in 3 groups.Setting: Orthopaedic and sports sciences research laboratory.Patients or Other Participants: 48 healthy adults free from back and lower extremity injuries.Intervention(s): Participants were randomly assigned to muscle hypertrophy training, muscle strength training, or the control group. Those in the training groups pursued training 3 times per week for 8 weeks.Main Outcome Measure(s): Magnetic resonance imaging and ultrasound cross-sectional area of the VMO, patellar tilt angle on magnetic resonance imaging, instrumented passive patellar mobility, and isometric knee extension torque of the dominant leg.Results: Participants in both training groups had comparable gains in VMO size, passive patellar stability, and knee extension force, all of which were greater than for the control group (P , .05).Conclusions: Both short-term muscle hypertrophy and strength training programs can reinforce the patellar stabilizers in previously untrained volunteers.

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