Effect of the vastus medialis obliquus on the patellofemoral joint

Abstract

In this study, the effect of dynamic stabilizers on the patellofemoral (PF) joint was investigated in normal volunteers (group I) and in patients with patellar pain (group II) or instability (group III) by using computed tomography (CT) analysis and integrated electromyography (iEMG) of the quadriceps muscle. Nine subjects (16 knees) from group I, 10 patients (12 knees) from group II and 8 patients (12 knees) from group III were included in the study. CT scans of the PF joint with quadriceps contracted (QC) and uncontracted (QU) and iEMG of vastus medialis obliquus (VMO), vastus lateralis (VL) and rectus femoris (RF) were obtained with the aid of a specially designed jig at 0 degree, 15 degrees, 30 degrees and 45 degrees of knee flexion. The same muscle contraction pattern simulating closed kinetic chain exercise was used for both CT and iEMG. The difference between the congruence angles (CA) and tilt angles (PTA) in QC and QU positions and VMO:VL ratio from the iEMG were calculated separately for each flexion angle. CA was increased in all groups with quadriceps contraction at 0 degree and 15 degrees of flexion. PTA was decreased in group I and increased in groups II and III with quadriceps contraction at the same flexion angles. This difference was statistically significant in group III at 0 degree and 15 degrees of flexion. Quadriceps contraction did not affect the patellar position significantly even in the instability group at 45 degrees of flexion. In all flexion angles the balanced VMO:VL activity ratio was observed only in group I. In the other groups, VL activity was higher than VMO activity except at 45 degrees of flexion. These findings do not support the hypothesis of dominant centralizing effect of VMO on the patella in extension, but the effect of the VMO may be more clearly demonstrated by measuring PTA in both QC and QU positions.

Avaliação eletromiográfica e ressonância magnética do joelho de indivíduos com síndrome da dor femoropatelar

“…The present study was performed with the quadriceps relaxed, and this may explain the absence of differences between the groups because, in Taskiran et al 33 , the PTA was lower with the quadriceps contracted in individuals with patellofemoral instability in relation to the control group. In contrast, Kujala et al 5 evaluated the PD in a control group during knee extension MVICs and compared the images with the quadriceps relaxed, finding no difference between them.…”

“…These results showed, therefore, that the patellar position was not correlated to the electrical activity. Taskiran et al 33 used computed tomography to analyze the PTA of the knee and EMG to analyze the VMO and VL in nine normal subjects (G1), 10 with knee pain (G2) and 8 with patellar luxation (G3). The results showed a decrease in PTA in G1 and an increase in G2 and G3 during quadriceps contraction at 0°, 15° and 45° of knee flexion.…”

Effect of knee joint angle on motor unit synchronization

“…25,26 Thus, precise coordination of the activity of the vasti is important in control of the patellofemoral joint. 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.…”

“…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. 18,30 The present data are consistent with the majority of studies that report no effect of knee angle on activity of the vasti muscles.…”

“…12 This is important if the subdivisions of the muscle are purported to have differences in function. 1 Different methods of recording and analysis are also used in various studies, such as action potential counts during an MVC, 1 VMO:VL ratio of integrated EMG, 29 or the average integrated EMG during weight bearing as a percentage of maximal voluntary contraction (MVC). 32,33 Although our results cannot be directly compared to previous data, analysis of motor unit synchronization between the vasti provides an alternative method to evaluate the coordination of activity between the muscles at different joint angles, and suggests that coordination is maintained throughout range of movement, contributing to resolution of the debate.…”