Glaviano 2016.

Methods	Double‐blinded, randomised sham‐controlled trial Trial protocol registration: not reported
Participants	Country: United States Setting: laboratory (single NMES session) Data collection period: not described Inclusion criteria: age between 15 and 65, atraumatic knee pain (greater than 3 months), pain with more than 2 of the following activities: jumping, kneeling, prolonged sitting, quadriceps contraction, running, squatting, or stair climbing or when pressure was placed on the patella. Participants were required to score less than 85 of 100 on the Anterior Knee Pain Scale. Exclusion criteria: previous knee surgery, ligamentous instability, meniscal injury, or other sources of anterior knee pain, such as patellar tendinitis, bursitis, or patella subluxation. Contraindications to electrical stimulation: implanted biomedical devices, history of neuropathy, muscular abnormality, hypersensitivity to electrical stimulation, or active infection where the electrodes would be placed. Mean duration of symptoms: not reported People who presented bilateral complaints were included, but only the most symptomatic knee was treated. Study participants: 22 people with patellofemoral pain assigned and assessed NMES group: n = 11 Sham group: n = 11 Mean age (SD): 26.0 (7.9) years Gender (number of women/men): 15/7
Interventions	Comparison: NMES versus placebo Treatment duration: single session (15‐minute treatment) Treatment setting: laboratory Details of interventions: NMES programme: PENS: biphasic asymmetric square‐wave pattern of 50‐hertz pulse frequency, 70‐microsecond phase duration, and 200‐millisecond stimulus train. 2 channels were used to deliver alternating patterns, mimicking the agonist‐antagonist muscle pattern that is seen in healthy people during functional tasks. Channel 1 consisted of 2 self adhesive electrodes positioned over the agonist muscles (gluteus medius and VMO), and channel 2 consisted of 2 electrodes positioned over the antagonist muscles (the middle of the adductor muscle group and the middle of the hamstrings muscle group). The patterned stimulus was a 200‐millisecond contraction to channel 1, a 200‐millisecond contraction to channel 2, and finally a 120‐millisecond contraction to channel 1. Participants were positioned on a treatment table with the hip and knee flexed to approximately 90º for the single 15‐minute treatment, which resulted in a strong motor contraction visible to the researcher. Sham group: Participants received a single 15‐minute treatment (identical device settings were applied); however, the amplitude was only increased to 1 mA, which is the minimum stimulus allowed for the device display to light up and activate the timer to replicate a true treatment, even though no participant could perceive stimulation. The electrodes were placed at the same muscles as described above. Participants were instructed that they were receiving a "subsensory" treatment. At the end of the intervention, the PENS electrodes were removed, and the participants were instructed to perform 2 functional movements. Outcome data were collected for both tasks. Single‐leg squat: the participant was instructed to stand on the injured leg and squat so that the knee was flexed to more than 60° and then return to the starting position. The participant was instructed to maintain the non‐standing limb at 90° of knee flexion for the duration of the task. The time to perform the task was standardised: 2 seconds to lower and 2 seconds to return to the starting position. Lateral step‐down: the participant stood on a step that was normalised to 10% of his or her height, lowered himself or herself until the contralateral heel touched a force plate, and then returned to the starting position. A 4‐second time period was also used for this task.
Outcomes	Outcomes analysed in the study and used in this review: Knee pain: VAS: participants placed a vertical mark on a 10‐centimetre VAS line for the pain they experienced during both tasks. Follow‐up assessments: immediately at the end of the single‐session treatment (after completing the single‐leg squat and lateral step‐down)
Notes	Description of condition: patellofemoral pain The trial authors provided additional information on random sequence generation, allocation concealment, and blinding (participants, personnel, and assessors) via email (12 August 2016).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Available information did not permit judgement.
Allocation concealment (selection bias)	Unclear risk	Quote: "One researcher concealed treatment interventions in envelopes, which were randomly allocated to participants before enrolment." The authors did not mention if the envelopes were sealed and opaque.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "sham controlled laboratory study" Since the authors did not exclude people who had received previous NMES therapy, it is difficult to affirm that the blinding was effective.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "At the conclusion of the 15‐minute treatment, electrodes were removed, the blinded researcher left the laboratory, and the primary researcher returned to the laboratory to conduct post‐intervention assessments" It is not clear if the outcome assessor was blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants completed the study.
Selective reporting (reporting bias)	High risk	No study protocol available. It is unclear if the results included all expected outcomes. This study did not consider adverse event as an outcome. Another report of this study that included a subgroup of 15 females presented the same baseline characteristics (age, height, mass, anterior knee pain score, and VAS pain knee) as those for the 22 participants in the study.
Other bias	Unclear risk	Although the baseline characteristics were balanced between groups, we are uncertain whether these are correct. The pain scores (1.9 in both groups) were below the threshold ("more than 2") for inclusion in the trial.