Lower Amplitude of the Hoffmann Reflex in Women With Patellofemoral Pain: Thinking Beyond Proximal, Local, and Distal Factors

Abstract

Objectives: To investigate whether vastus medialis (VM) Hoffmann reflexes (H-reflexes) differ on the basis of the presence or absence of patellofemoral pain (PFP) and to assess the capability of VM H-reflex measurements in accurately discriminating between women with and without PFP.

Design: Cross-sectional study.

Setting: Laboratory of biomechanics and motor control.

Participants: Women (N=30) aged 18 to 35 years were recruited, consisting of 2 groups: women with PFP (n=15) and asymptomatic controls (n=15).

Interventions: Not applicable.

Main outcome measures: Maximum evoked responses were obtained by electrical stimulation applied to the femoral nerve, and peak-to-peak amplitudes of maximal Hoffmann reflex (Hmax) and maximal motor wave (Mmax) ratios were calculated. Independent samples t tests were performed to identify differences between groups, and a receiver operating characteristic curve was constructed to assess the discriminatory capability of VM H-reflex measurements.

Results: VM Hmax/Mmax ratios were significantly lower in participants with PFP than in pain-free participants (P=.007). In addition, the VM Hmax/Mmax ratios presented large and balanced discriminatory capability values (sensitivity, 73%; specificity, 67%).

Conclusions: This study is the first to show that VM H-reflexes are lower in women with PFP than in asymptomatic controls. Therefore, increasing the excitation of the spinal cord in PFP participants may be essential to maintaining the gains acquired during the rehabilitation programs.

Keywords: H-Reflex; Knee; Patellofemoral pain syndrome; Rehabilitation; Spinal cord.