Background and Objectives: Transcutaneous electrical stimulation of low- and medium-frequency currents is commonly used in pain management. Interferential current (IFC) therapy, a medium frequency alternating current therapy that reportedly reduces skin impedance, can reach deeper tissues. IFC therapy can provide several different treatment possibilities by adjusting its parameters (carrier frequency, amplitudemodulated frequency, sweep frequency, sweep mode or swing pattern, type of application (bipolar or quadripolar), time of application and intensity). The objective of this review article is to discuss the literature findings on the analgesic efficacy of IFC therapy. Conclusions: According to the literature, IFC therapy shows significant analgesic effects in patients with neck pain, low back pain, knee osteoarthritis and post-operative knee pain. Most of the IFC parameters seem not to influence its analgesic effects. We encourage further studies to investigate the mechanism of action of IFC therapy.

Objective: Given the complex and unclear etiology of neck pain, it is important to understand the differences in central sensitization as well as psychosocial factors in individuals with chronic neck pain and healthy controls. The purpose of this study was to benchmark differences in central sensitization, psychosocial factors, and range of motion between people with nonspecific chronic neck pain and healthy controls and to analyze the correlation between pain intensity, neck disability, and psychosocial factors in people with chronic neck pain. Methods: Thirty individuals with chronic neck pain and 30 healthy controls were included in this case–control study. Outcome measures were as follows: central sensitization (pressure pain threshold, temporal summation, and conditioned pain modulation), psychosocial factors (depressive symptoms, pain catastrophizing, and quality of life), and active cervical range of motion. Results: People with neck pain had lower local pressure pain threshold, a decrease in conditioned pain modulation, more depressive symptoms, greater pain catastrophizing, lower quality of life, and reduced range of motion for neck rotation compared with healthy controls. In people with neck pain, moderate correlations were observed between pain intensity and quality of life (ρ = −0.479), disability and pain catastrophizing (ρ = 0.379), and disability and quality of life (ρ = −0.456). Conclusion: People with neck pain have local hyperalgesia, impaired conditioning pain modulation, depressive symptoms, pain catastrophizing, low quality of life, and reduced active range of motion during neck rotation, which should be taken into account during assessment and treatment. Impact: This study shows that important outcomes, such as central sensitization and psychosocial factors, should be considered during assessment and treatment of individuals with nonspecific chronic neck pain. In addition, pain intensity and neck disability are correlated with psychosocial factors.

To evaluate the effects of interferential current and photobiomodulation in patients with knee osteoarthritis. A randomized, placebo-controlled, double-blind clinical trial. Physiotherapy Clinic of City University of São Paulo. A total of 184 patients with knee osteoarthritis were recruited and, of these, 168 were included and randomized into four groups with 42 each: interferential current, photobiomodulation, interferential current plus photobiomodulation or placebo groups. One hundred and sixty-four patients completed the study. Patients received 12 sessions (three times a week) of treatment: 30 minutes of interferential current (active or placebo) followed by photobiomodulation (active or placebo). Primary outcome: pain intensity at rest and during movement (numeric rating scale) after 12 sessions. Secondary outcomes: functional capacity (Timed Up & Go and Sit and Lift tests and Lequesne and WOMAC questionnaires), pressure pain threshold, conditioned pain modulation, and muscle strength production (isokinetic evaluation). Patients were assessed at baseline, after 12 sessions, and three and six months after the end of the treatment. Interferential current plus photobiomodulation reduced pain intensity at rest and during movement compared to placebo and interferential current at all time points (P < 0.05). Photobiomodulation reduced pain intensity at rest compared to placebo at all time points (P < 0.05) and compared to interferential current at six months follow-up (P < 0.05). Photobiomodulation reduced pain intensity during movement compared to placebo at six months follow-up (P < 0.05). Interferential current plus photobiomodulation or isolated photobiomodulation improve pain intensity in knee osteoarthritis.

Objective: To compare the segmental and extrasegmental hypoalgesic effects of TENS, IFC and Aussie current on pressure pain threshold (PPT) during and after stimulation in healthy subjects. The second objective was to compare the sensory comfort related to electrical stimulation. Material and Methods: 120 healthy subjects were randomized in TENS, IFC, Aussie current or placebo groups. The electrical stimulation was administered on the forearm. The PPT was measured on the forearm (segmental measure) and on the lower leg (extrasegmental measure) by an algometer at baseline, during and after stimulation of the forearm, and the sensory comfort in relation to electrical stimulation was measured with a visual analogue scale. Statistical analysis was performed using linear mixed models for PPT analysis and one-way ANOVA for sensory comfort analysis. Results: The TENS, IFC and Aussie current increased the segmental and extrasegmental PPTs during application of current compared to the placebo. The PPTs measures and sensory comfort were not significantly different between the TENS, IFC and Aussie current groups. Conclusions: Segmental and extrasegmental hypoalgesic effects may be produced using TENS, IFC or Aussie currents in healthy subjects. Furthermore, all of them presented a similar sensory comfort.