Table 1. Methodological characteristics and evidence observed for determining the use of Neuromuscular Electrical Stimulation to gain strength and reduce pain in patients with patellofemoral dysfunction.

Authors Year of publication	Study design	Study population/Place	Identification	Results	Discussion	Remarks
Jenniferet al.19,in 2011	Intervention	Nineteen women with PFD.	An 8-week muscle strengthening program on women with PFD.	Strengthening of the hip muscles, improves knee stability reducing pain and improving functional capacity.	An 8-week rehabilitation program improves the neuromuscular control of the hip muscles and reduces PFD symptoms.	Muscle strengthening is associated with improvement of PFD.
Santoset al.16,in 2011	Controlled intervention	Twenty-seven female individuals students from UFSCAR	Fifteen without PFD and 12 presented PFD.	There is a difference in hip muscle activation order in individuals with and without PFD.	In individuals with PFD the activation order started with VLL followed by VLO and VMO, while in individuals without PFD the order was inverted, starting with VMO, followed by VLO and ending with VLL.	This study shows that the imbalance between the lateral and medial muscles will predispose to the onset of PFD.
Billot et al.27, 2010	Controlled intervention	Twenty soccer players, allocated in 2 groups. (G1) performed only soccer training while (G2) had soccer training plus electrical stimulation 3 times a week for 12 minutes.	Soccer players from Faculdade de Ciências do Esporte French Football Federation.	There was an increase in eccentric torque in the third week (+ 11.5 +- 10.4%, p <0.01) and in the fifth week (22.1 +- 16.4% p <0.001). There was an increase in isometric contraction in the third and fifth weeks (16.3 +- 21.3, p <0.01 and 27.1 + - 22.6% p <0.001, respectively).	The results of the present study showed a smaller increase in strength than that observed previously in ice hockey players in eccentric conditions (12 vs. 24% in soccer players and ice hockey players, respectively).	A 3-5 week NMES training program appears to improve strength and the specific functions of soccer in the preseason and during the season, and to lessen or eliminate the effects of detraining in injured athletes.
Duarte et al.23, 2009	Controlled intervention	Thirty female patients who presented shortening of the ischiotibial muscles.	Female academics, from Universidade Estadual de Goiás	In relation to hip flexion in MID, the control group had a relative gain of 0.25 %, manual passive stretching achieved a relative gain of 29.65 %, stretching associated with NMES had a relative gain of 61.89 %.	It is evidenced that the increase in the range of motion of a joint is only possible by means of the application of a program of planned and regular exercises, and the muscle stretching method associated with electrical stimulation offers advantages over the other methods.	Despite the interesting results, it is suggested that new surveys be conducted with a larger sample, over longer periods of time, with individuals of both sexes and from different age brackets.
Bily et al.25, 2008	Controlled intervention	Thirty-eight patients with PFD (14 men and 24 women), divided into 2 groups. (G1) performed only exercises and (G2) Exercises + NMES	Supervised home based treatment	Both groups achieved a decrease in pain and an increase in the quadriceps torque, with no statistical difference between G1 and G2.	The improvements observed in isometric conditions corroborated the work of Gondin et al., who observed a 15% increase in isometric maximum voluntary contraction of the quadriceps muscles after 4 weeks of NMES training that can be explained by the fact that the angular position during the NMES sessions was the same as the isometric test position (i.e., 60º)	Further investigations should address different aspects of training exercises, including measures to discover potential neurophysiological effects of exercise and EMS.
Cabral et al.17, 2008	Controlled intervention	Twenty female patients with PFD (10 performed hip MS in OKC and 10 in CKC).	Study carried out at the Clinical Physiotherapy Investigation and Electromyography Laboratory of the Department of Physiotherapy, Speech and Language Therapy and Occupational Therapy of FMUSP	The analysis of the demographic data did not evidence a statistically significant difference between the groups. G1 and G2 had a statistically significant difference P<0.05 in most of the variables after treatment.	Sacco et al studied the misalignments of patients with PFS, obtaining results similar to this study before the treatment, and observed a decrease in the alterations after the treatment.	The strengthening of the quadriceps muscle enabled improvements in the main signs and symptoms. Yet in relation to realignment of the lower limb, the treatments did not prove efficient.
Nakagawaet al.18, 2008	Blind controlled intervention	Fourteen patients (10 women and 4 men) diagnosed with patellofemoral pain syndrome.	During the week one session was held at the rehabilitation clinic and four sessions at home.	The intervention group achieved an improvement in torque during knee extension, in the electromyographic activity of the gluteus medius during maximum isometric contraction and in the symptomatology of the pain perceived, while the control group achieved improvement only in torque for knee extension.	Recent studies have reported significant losses in hip abduction and in lateral rotation strength, and suggest that strengthening exercises for the hip muscles may be an important factor in pain management.	New surveys should be carried out with a larger sample and a longer follow-up period.
Augustoet al.14, 2008	Blind controlled intervention	Eighteen healthy female volunteers, with an analysis of VMO vs. VL activation, before and after neuromuscular electrical stimulation.	The study was carried out on healthy subjects at UFRN in the Physiotherapy Department	The results showed an increase in activation of the VMO muscle from 458uV to 580uV after the use of NMES.	The literature states that one of the factors for PFD is poor patellar alignment. Bohannon et al showed that NMES prevented lateral dislocation of the patella.	EENM has proven itself to be an important technique in the treatment of PFPS, providing this is secondary to muscle imbalance.
Avila et al.24, 2008	Controlled intervention	Twenty healthy students of both sexes	Study carried out at the Laboratory of Muscle Plasticity in the Physiotherapy Department (UFSCar) and in the Physiotherapy Department of (UFRN).	Men and women increased their peak torque in both limbs with no difference between Ex andEx + NMES.	The study showed that NMES associated with concentric knee exercises did not produce any additional torque increase, in comparison with only concentric exercises in healthy men and women.	New studies should be conducted with a larger population and different velocities.
Pelizzariet al.12, 2008	Controlled intervention	Eight dogs with induced muscular atrophy	Study carried out on the dogs from the Central Vivarium of Universidade Federal de Santa Maria	As regards the morphometry of the fibers of the vastus lateralis muscle, a higher value was observed in the treated group than in the control group.	It is suggested that the presence of adipocytes on the histology slides may explain the increase in the perimeter, when evaluated in this manner, making this method subjective.	Medium-frequency NMES produces gain of muscle mass in dog with induced muscular atrophy.
Santoset al.16, 2008	Controlled intervention	Twenty sedentary women, divided into 2 groups, where group (A) received only passive electrical stimulation, while group (B) performed resistance exercises.	Voluntary, right-handed, sedentary women in Maceió, in the state of Alagoas	Group A did not achieve a significant increase in strength or in the perimeter of the quadriceps muscles, while group B achieved a significant increase in the strength and perimeter of the quadriceps.	The study showed that the resistance exercise of flexo-extension of the knees is effective in promoting an improvement in muscle mass and strength, contrary to electrical stimulation using an apparatus for domestic use, which did not achieve the same results.	The results suggest that electrical stimulation could have been effective in increasing muscle strength measured by the dynamometer if the numbers of sessions had been increased.
Bevilaqua-Grossiet al.15, 2008	Controlled intervention	Twenty-four sedentary female patients, 12 healthy (control) and 12 with PFPS, where the reflex response time of VMO, VLO and VLL was evaluated.	Study carried out at the FMRP–USP, Campus Universitário.	There was no difference between healthy individuals and those with PFPS, yet there was a significant difference between VLO and VMO activation times.	In the discussion the authors mention that in the individuals with PFPS, the VL muscle presents a shorter reflex response time than the VMO muscle.	No decision can be made on a basis of the reflex response time, since both healthy individuals and those with PFPS exhibit an imbalance between VMO and VLO.
Matheuset al.10, 2007	Controlled intervention	Sixty female rats, divided into 6 groups, G1 – control, G2 – electrically stimulated, G3 – immobilized in shortened position, G4 – immobilized in stretched position, G5 – immobilized in shortened position and electrically stimulated G6 – immobilized in stretched position and electrically stimulated.	Carried out at the Vivarium of the Bioengineering Laboratory ofFMRP–USP.	Results of the ALP (stretching at the limit of proportionality) Significant differences were observed between G1 and the immobilized groups; in comparing G3 and G5, significant differences were also observed. Results of the CLP – carga no limite de proporcionalidade (load at the limit of proportionality)Significant differences were observed between groups G1 and G2 and the immobilized groups; in comparing groups G3 and G5 it was also possible to observe significant differences, which did not occur between G4 and G6.	In this study, just as in the study by Järvinen et al, the gastrocnemius muscles immobilized in shortened position (SP) had a greater reduction of the properties than those immobilized in a lengthened position (LP).	The study suggests that the immobilization of the muscles in a stretched position delays the atrophy process and that electrical stimulation, carried out during immobilization, contributes to the prevention of mechanical properties during the immobilization period.
Silva et al.12, 2007	Controlled intervention	Nine male individuals who had been practicing bodybuilding for more than 2 years, 5 of whom were from the Special Operations Battalion and 4 frequented a gym).	Carried out at the Special Operations Battalion (BOE) of Passo Fundo, Rio Grande do Sul and at a fitness center from the south side of Porto Alegre.	The group that associated strength training with NMES achieved a significant increase in strength and in the thigh perimeter when compared with the group that performed only exercises.	Grillo et al inform that many protocols used in electrical stimulation programs contain discrepancies. Alonso et al reports that the application of NMES on the thigh muscles produces an increase in muscle strength as well as an increase in the thigh perimeter.	It was verified that the application of neuromuscular electrical stimulation is an efficient method to assist in muscle strengthening. However, further studies are necessary.
Belchioret al.20, 2006	Controlled intervention	Twenty female individuals (10 symptomatic and 10 asymptomatic) where a difference was observed in the quadriceps angle of these 2 groups.		The mean values of the Q angle for the asymptomatic subjects were 17.15º in relaxation and 14.5º in MVIC, while the symptomatic subjects presented 21.45º and 15.8º respectively.	Keeping track of the analysis of results, it is possible to visualize the difference in magnitude of the Q angle between symptomatic and asymptomatic individuals, in a state of relaxation (p = 0.004).	It is believed that Maximum Voluntary Isometric Contraction (MVIC), associated with exercise performed with Straight Leg Raise (SLR), might minimize poor patellar alignment.
Bevilaqua-Grossiet al.21, 2005	Controlled intervention	Thirty female patients (15 clinically normal and 15 with patellofemoral pain syndrome)	The study was conducted at FMRP–USP, Campus Universitário	The control group at 45º obtained greater electromyographic activity of the VLL muscle when compared with VMO and VLO. At 60º there was no difference. In the group with PFPS, during the exercises at 45º and 60º no difference was obtained between VMO, VLO and VL.	Isometric exercises at an angle of 45º and 60º activate equally the musculature, vastus medialis obliquus, vastus lateralis and vastus lateralis obliquus.	New studies should be carried out to compare the electrical activity of the VMO, VLL and VLO muscles so as to favour the preparation of physiotherapy protocols.

UFRN: Universidade Federal do Rio Grande do Norte, Rio Grande do Norte, Brasil. UFSCar: Universidade Federal de São Carlos, São Paulo, Brasil. FMRP-USP: Faculdade de Medicina de Ribeirão Preto da USP, São Paulo, Brasil.