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A dysfunction of the quadriceps muscle group has often been suggested to play an important role in the pathophysiology of patellofemoral pain (PFP). However, consensus is lacking regarding the quadriceps recruitment pattern of patients with PFP. The aim of this study was to examine by muscle functional magnetic resonance imaging if patients with PFP actually exhibit an altered activation of the muscles that play a significant role in the dynamic balance of the patella.Forty-six patients with PFP (25 female and 21 male, mean ± SD age = 25.0 ± 7.4 yr) and 30 healthy control subjects (17 female and 13 male, mean ± SD age = 21.6 ± 4.5 yr) underwent MRI of the quadriceps before and immediately after a squat exercise. The transverse relaxation time (T2) and the T2 shift were calculated for the vasti muscles.There were no significant differences in the T2 values at rest and the T2 shift values between the patient and the control groups, except for the T2 rest value of the VMVI of females (P = 0.007). The T2 shift of the VL was significantly smaller than the T2 shift of the VMVI in both study groups (male P < 0.001 and female P = 0.044), while in females, the T2 shift of the VMO was also significantly smaller than the T2 shift of the VMVI (P = 0.027).The activation pattern of the quadriceps is not altered in patients with PFP for both males and females. Because the relative contribution of the quadriceps muscles to a functional activity has not been modified, there is no evidence for quadriceps dysfunction.