Delayed onset of electromyographic activity of vastus medialis obliquus relative to vastus lateralis in subjects with patellofemoral pain syndrome

Análise do tempo de resposta reflexa dos músculos estabilizadores patelares em indivíduos com síndrome da dor patelofemural

“…According to Cowan et al 7 , the VMO presents a biomechanical advantage over the VL due to the oblique orientation of its muscle fibers. However, the neuromuscular response of the VMO may relate to the attempt by this stabilizer to resist the lateral patellar forces, given that the patella tends to lateralize.…”

“…Some studies have analyzed the beginning of voluntary electrical activity of the median and lateral stabilizing muscles of the patella in clinically healthy and individuals with PPS, and have demonstrated synchronism of these muscles under different functional conditions 13 . However, other authors have not observed this synchronism when comparing the beginning of the electrical activity of the (VMO) and vastus lateralis (VL) muscles between normal individuals and those with PPS 2,7 . The beginning of this activity has been used to evaluate the neuromuscular response time of the patellar stabilizing muscles and also how the effect of carrying out treatment protocols on individuals with PPS influences this parameter 12,14,15 .…”

“…This syndrome is present in approximately 25% of orthopedic diagnoses 4 and is defined as a pain at the front of the knee and/or rear of the patella [4][5][6] . It is aggravated during physical activities and when going up and down stairs, walking on slopes, squatting and remaining seated for long periods of time 7 .…”

Effect of knee joint angle on motor unit synchronization

“…A number of studies have reported that the ratio of the EMG activity of VMO relative to VL in people without knee pain is approximately 1:1 throughout knee range of movement, [26][27][28][29] and that the relative onset of VMO and VL EMG is simultaneous in people with no knee pain during functional tasks. 18,26,30,31 Furthermore, a change in relative onset of activity between these muscles has been associated with dysfunction. For example, people with PFP have a reduced VMO:VL ratio, 29 and the onset of VMO EMG activity is delayed relative to VL in functional tasks.…”

“…Wire electrodes were inserted into standard sites along the muscle: distal VL (VLd) 100 mm superior and 60 to 80 mm lateral to the superior border of the patella, angled 158 to a line connecting the superior pole of the patella and the anterior superior iliac spine; and proximal VL (VLp) 100 mm more proximally along the muscle belly. 18 The intramuscular electrodes were referenced to a single surface electrode (20 mm Ag/AgCl disc, GrassTelefactor) placed 10 mm laterally to the wire. A ground electrode was placed over the anterior tibia $ 50 mm distal to the inferior pole of the patella.…”