Comparison of Gluteus Medius Muscle Activation in Females with and without Patellofemoral Pain
Females with patellofemoral pain (PFP) commonly have hip muscle weakness in comparison to females without PFP. One underlying mechanism for this muscle weakness is inhibition. Although the presence of muscle weakness is well documented in females with PFP, few authors have investigated gluteus medius inhibition in this population. Females are twice as likely to suffer from PFP when compared to males, therefore this study will focus on the female population. To compare voluntary activation of the gluteus medius between females with and without PFP. Case-control study. Laboratory. 28 female participants: 13 pain-free controls (age = 21.6 ± 3.6 years, height = 1.66 ± 0.06 m, mass = 65.4 ± 11.3 kg) and 15 with PFP (age = 22.3 ± 3.2 years, height = 1.66 ± 0.07 m, mass = 75.3 ± 22.6 kg, duration of pain = 3.5-96 months). Standing hip abduction normalized strength (N·m/kg), superimposed burst force and gluteus medius central activation ratio (CAR). Linear modeling was utilized to compare forces and CAR between groups while controlling for age, mass, and hip abduction force. Females with PFP had lower gluteus medius CAR than controls. Overall, after controlling for participant age, mass and gluteus medius MVIC, the PFP group had an average gluteus medius CAR 2.5% lower than the pain-free control group (Control= 98.4±.01%, PFP=95.9±.65%, p=.004). Females with PFP had reduced voluntary activation of the gluteus medius, when assessed with a superimposed burst. Due to the wide range of CAR values found (74-99%), inhibition was present in some of the participants. This provides evidence that assessment of gluteal voluntary activation could assist with targeted treatment programs for individuals presenting with PFP.ABSTRACT
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