The Effect of Exercise and Electrical Muscle Stimulation on the Architecture of the Vastus Medialis Oblique - The ‘Empi’ Electrotherapy System

Study Design: Asymptomatic volunteers underwent a vastus medialis oblique (VMO) muscle-strengthening programme, in both lower limbs. Neuro-muscular electrical stimulation (NMES) was applied to one limb, with the contralateral limb acting as the control.

Background: The usual first line treatment for patellofemoral pain is physiotherapy, targeting the vastus medialis oblique (VMO), with or without NMES. There is a lack of data on the effect of NMES on the architecture of the VMO. Objectives: To investigate the effect of targeted exercises, with and without NMES, on the fiber angle and insertion level of the VMO.

Methods: Twenty-four asymptomatic female volunteers undertook a six-week muscle-strengthening programme targeting the VMO, on both lower limbs. An Empi electrical stimulator was used on one limb, with the other limb as the control. The VMO fiber angle with respect to the femoral axis, and insertion level on the medial border of the patella, before and after the exercise programme, were measured with ultrasound. Patellar length was measured, and the insertion ratio (insertion length/patella length*100) was calculated.

Results: Mean VMO fiber angle increase with and without NMES was 7.33 and 3.95, respectively. There was a significant increase in the insertion level in both limbs, but no significant difference between the stimulated and unstimulated limbs. There was a significant change in insertion ratio in the unstimulated limb. An inverse correlation was found between initial fiber angle and fiber angle change.

Conclusion: Electrical stimulation significantly enhances the effects of targeted exercises on the VMO fiber angle.

Keywords: Anatomy/lower extremities; Electrostimulation/electrotherapy; Patellofemoral joint