Background: manual therapy (MT) has been shown to have positive effects in patients with osteoarthritis (OA)-related pain, and its use in clinical settings is recommended. However, the mechanisms of action for how these positive effects occur are not yet well understood. The aim of the present study was to investigate the influence of MT treatment on facilitatory nociception and endogenous pain modulation in patients with knee OA related pain. Methods: Twenty-eight patients with knee OA were included in this study. Pain intensity using the numerical pain rating scale (NPRS), temporal summation (TS), conditioned pain modulation (CPM), and local (knee) and distant (elbow) hyperalgesia through the pressure pain threshold (PPT), were assessed to evaluate the pain modulatory system. Patients underwent four sessions of MT treatments within 3 weeks and were evaluated at the baseline, after the first session and after the fourth session. Results: the MT treatment reduced knee pain after the first session (p = 0.03) and after the fourth session (p = 0.04). TS decreased significantly after the fourth session of MT (p = 0.02), while a significant increase in the CPM assessment was detected after the fourth session (p = 0.05). No significant changes in the PPT over the knee and elbow were found in the follow-ups. Conclusions: The results from our study suggest that MT might be an effective and safe method for improving pain and for decreasing temporal summation.

Background: Transcranial direct current stimulation (tDCS) of the motor cortex (M1) produces short-term inhibition of pain. Unihemispheric concurrent dual-site tDCS (UHCDS-tDCS) over the M1 and dorsolateral prefrontal cortex (DLPFC) has greater effects on cortical excitability than when applied alone, although its effect on pain is unknown. The aim of this study was to test if anodal UHCDS-tDCS over the M1 and DLPFC in healthy participants could potentiate conditioned pain modulation (CPM) and diminish pain temporal summation (TS). Methods: Thirty participants were randomized to receive a sequence of UHCDS-tDCS, M1-tDCS and sham-tDCS. A 20 min 0.1 mA/cm2 anodal or sham-tDCS intervention was applied to each participant during three test sessions, according to a triple-blind cross-over trial design. For the assessment of pain processing before and after tDCS intervention, the following tests were performed: tourniquet conditioned pain modulation (CPM), pressure pain temporal summation (TS), pressure pain thresholds (PPTs), pressure pain tolerance, mechanosensitivity and cold hyperalgesia. Motor function before and after tDCS intervention was assessed with a dynamometer to measure maximal isometric grip strength. Results: No statistically significant differences were found between groups for CPM, pressure pain TS, PPT, pressure pain tolerance, neural mechanosensitivity, cold hyperalgesia or grip strength (p > 0.05). Conclusions: Neither UHCDS-tDCS nor M1-tDCS facilitated CPM or inhibited TS in healthy subjects following one intervention session.

Objectives The main aim was to determine the effects of percutaneous (PENS) and transcutaneous (TENS) electrical nerve stimulation on endogenous pain mechanisms in patients with musculoskeletal pain. Design A systematic review and meta-analysis. Methods The search was conducted on March 1, 2022, in EMBASE, CINAHL, PubMed, PEDro, Cochrane Library, Web of Science, Medline and SCOPUS databases. Randomized controlled trials (RCTs) comparing the use of transcutaneous or percutaneous electrostimulation with a placebo, control group or standard treatment in patients with musculoskeletal pain were included. Outcome measurements were QST somatosensory variables like pain threshold at pressure (PPT), conditioned pain modulation (CPM) and temporal summation of pain (TSP). The pooled data were evaluated with Review Manager 5.4. Results Twenty-four RCTs (N = 24) were included in the qualitative analysis and 23 in the meta-analysis. The immediate effects of PENS and TENS on local PPTs were significant with a moderate effect size (SMD 0.53, 95% CI: 0.34 to 0.72, p < 0.00001). When only studies with a lower risk of bias were analyzed, the heterogeneity from I2=58% (P < 0.00001) to I2=15% (P = 0.01) and a decrease in the overall effect was observed (SMD 0.33, 95% CI: 0.7 to 0.58). The short-term effects on local PPTs were not significant when compared to the control group (P = 0.13). The mid-term effects on local PPTs were significant showing a large effect size (SMD 0.55, 95% CI: 0.9 to 1.00, p = 0.02). The immediate effects on CPM were significant with a large effect size (SMD 0.94, 95% CI: 0.48 to 1.41, p < 0.0001). Conclusion PENS and TENS have a mild-moderate immediate effect on local mechanical hyperalgesia in patients with musculoskeletal pain. It appears that these effects are not sustained over time. Analyses suggest an effect on central pain mechanisms producing a moderate increase in remote PPT and in the case of PENS on CPM, but further studies are needed to draw clearer conclusions.