Background and Aim: It is believed that dysfunction of the quadriceps muscle can be considered as one of the cause of patellofemoral pain syndrome with great emphasis placed on vastus medialis oblique and vastus lateralis muscles imbalance. The purpose of this study was to compare the EMG activity ratio of vastus medialis oblique: vastus lateralis muscles in athletes with and without patellofemoral pain syndrome.Materials and Methods: 12 athletes with Patellofemoral pain syndrome (age 23.23±3.70 year, height 179±7.00 cm, and weight 73.86±12.00kg) and 12 healthy male athletes (age 23.45±3.17 year, height 177±4.00 cm, and weight 68.84±8.53 kg) Participated in a quasi-experimental study. Numerical Pain Rating scale was used to assess the pain. EMG activity of vastus medialis oblique and vastus lateralis muscles during dynamic postural perturbation were collected using a 16- channel EMG System. To data wasanalysed by Independent-t test at the significance level was set as P£0.05.Results: The mean vastus medialis oblique: vastus lateralis EMG activity ratio in athletes with patellofemoral pain syndrome were less than control group. No significant difference was observed in the vastus medialis oblique: vastus lateralis EMG activity ratio between two groups during forward perturbation (p=0.56) and backward perturbation (p=0.52).Conclusion: Our findings suggest that vastus medialis oblique: vastus lateralis ratio was not differe between athletes with and without patellofemoral pain syndrome in postural dynamic perturbation and it is likely that long-term pain cause’s muscular balance reactions adaptation in athletes with patellofemoral pain syndrome. The results of this study would be useful for therapists to identify changes in motor control strategies and in a rehabilitation program design for athletes with patellofemoral pain syndrome.

Purpose: Strengthening of the VMO has been suggested as a treatment technique for the PFPS, as the weakness of this component of the quadriceps is one of the reasons of the mal alignment of the patella. Therefore, attempts have been made selectively to strengthen the VMO.Materials and Methods: We chose three common therapeutic exercises for the PFPS in the open kinetic chain.The EMG activity of the VMO and VL were evaluated in the dominant lower limb, during three training programs in three experimental groups and a control group. Eight healthy women volunteers, aged from 20-30 years(X=24.94, SD=I.97), were studied in each group (Total= 32 subjects). The characteristics of training programs were as follows: The first experimental group: quadriceps setting with dorsiflexion of the foot (30 times per day, three times per week, lasting 4 weeks). The second experimental group: SLR with lateral rotation of the femur (according to Delorm-Watkins training program, three times per week, lasting 4 weeks). The third experimental group: terminal extension of the knee (0-30 degrees) with medial rotation of tibia in the special splint for the isometric contraction of quadriceps (according to Delorm-Watkins training program, three times per week, lasting 4 weeks). The control group. The EMG activity of VMO and VL muscles were recorded as the pre-test, mid-test, and post-test for 12 seconds and the average rectified value (ARV) of the power spectrum of the EMG signal was used to evaluate the muscles" activities.Results: Statistical analysis showed that in the first group, the ARV of the VMO was increased in the I2th session compared to the 6th session. The ARV of the VL had no significant difference during the training sessions. In the second group, the ARV of the VMO and VL had no significant difference during the training sessions. In the third group, the ARV of the VMO showed a significant increase between the 12th and 6th sessions and the 12th and 1st sessions. In addition, the VMO: VL IEMG ratio, in the second and third groups was increased significantly between the 12th and 1st sessions.Conclusions: The results suggest that the VMO can be selectively strengthened by performing the SLR with the LR of the femur and the SAQ with the MR of the tibia.

Background: The purpose of this study was to investigate the ratio of Electromyography (EMG) activities of the vastus medial is obliqus (VMO) and vastus lateralis (VL) within seven angles of knee joint range of motion using isometric contraction in open kinetic chain (OKC) and closed kinetic chain (CKC). Methods: The dominant knees of 44 healthy female subjects (mean age: 24.84 with range: 20-30 years old) were analyzed. Surface electrode pairs were attached over the VMO and VL by using Basmajian methods. The EMG biofeedback data was collected while the subject performed isometric contraction on isometric and squat exercise within 7 degrees (0° to 90°) with 15° intervals of knee flexion angle. Results: Paired T-test and ANOVA were performed between variables. Results demonstrated that in this study there are significant differences: I) between OKC and CKC exercise in 0°, 15°, and 30° of knee flex ion, II) between all angles in CKC except: 0-15°,0-30°,0-45°, 15-30°,60-75°, and 75-90°, and III) between 15-60°, 30- 60°,45-60°, and 60-90° in OKC (p<0.001). As a result in OKC and CKC respectively, 60° and 15° angles of knee flexion were most sufficient positions (i.e. increased VMONL activities ratios), -15° and 90° of knee flexion were the most insufficient positions and arc of movement between 45- 75° and 0-30° was considered as the most sufficient arc of movement.Conclusion: As the result of this research and biomechanical and neuro-physiological viewpoints, emphasized in the literature, our recommendations are: in early phase or in early sessions of treatment of patellofemoral joint dysfunction, treatment exercise done in CKC & sufficient position and after progression of the patient's condition, OKC exercises could also be considered.

Objective: Patellar maltracking is one of the main causes of patellofemoral joint pain. This tracking dysfunction is mainly due to lock of a precise neuromuscular control between two parts of quadriceps muscle vastus medialis oblique (VMO) and vastus lateralis (VL). The ratio between electrical activity VMONL muscles is considered as an index for comparison between normal subjects and with those with patellofemoral pain. The purposes of this study are to compare the VMONL activity ratio in active and reactive movement patterns.Methods: This quasi-experimental study was conducted on a group of 30 healthy men as a control group and 30 patients with patellofemoral pain as an experimental group. These two groups were non-probably assigned, conveniently sampled and randomly asked to perform movement patterns test. During these tests, electromyographic activity of the muscles were normalized and integrated to absolute values. Movement pattern tests include maximum isometric contraction of quadriceps muscle at 60 degree of knee flexion; active movement patterns consist of forward step up (FSU) and lateral step up (LSD), and reactive movement patterns that consist of angular perturbation of ankle and perturbation of waist.Results: in healthy subjects VMONL ratio in active and reactive movement patterns was significantly greater than isometric contraction (P<0.05). Also this ratio was significantly greater in upward phase of FSU and LSU compared to downward phase. There was no precise and clear relationship between muscle activity ratios in different movement patterns. Comparison between control and experimental groups revealed the greatest significant difference only in active and isometric movement patterns. Conclusion: results indicate that VMONL activity ratio in normal patients has no relationship with the direction and location of perturbation but conversely is task-dependent to direction and location of perturbation in patients with patellofemoral pain.

Background and Aims: In patients with lateral patellofemoral compression syndrome, the vastus medialis muscle is weaker than the vastus lateralis muscle. The purpose of the present study was to investigate the effect of an exercise protocol focusing on vastus medialis activation on the electrical activity and cross-sectional areas of the vastus medialis and vastus lateralis muscles. Materials and Methods: In the current study, 30 females with lateral patellofemoral compression syndrome, aged 25. 4± 5. 7, were selected and randomly divided into two groups. The experimental group participated in isokinetic knee extension exercises at terminal 30° extension arc with maximal external rotation of the leg for eight weeks. The control group did not participate in any regular exercise. Before and after the intervention, the cross sectional areas and electrical activities of the vastus medialis and vastus lateralis muscles were measured using ultrasonography and electromyography. Data were analyzed running independent and paired t-tests at the significance level of P<0. 05. Results: There were no significant differences in any of the variables between the two groups before intervention (P<0. 05). But after the intervention, the vastus medialis/vastus lateralis activity and cross-sectional area ratio in the experimental group were found to be significantly higher than those of the control group (P<0. 001). Conclusion: According to the results, using isokinetic knee extension exercises can selectively strengthen the vastus medialis muscle and reduce the imbalance between vastus medialis and lateralis muscles in patients with lateral patellofemoral compression syndrome.