# Transcranial Direct Current Stimulation in the Treatment of Chronic Knee Pain: A Scoping Review
## 3 Results  
Below is the PRISMA 2020 flow diagram (Figure 1); from 135 records identified in the initial literature search, 124 were excluded and 11 articles were included (Tables 1 and 2). Legends: BPI: Brief Pain Inventory, DPIS: Descending Pain Inhibitory System, fNIRS: Functional Near-Infrared Spectroscopy, IL-6, IL-10, TNF-\(\alpha\): Interleukin-6, Interleukin-10, Tumor Necrosis Factor-alpha, KOA: Knee Osteoarthritis, QST: Quantitative Sensory Testing, RCT: Randomized Controlled Trial, tDCS: Transcranial Direct Current Stimulation, TENS: Transcutaneous Electrical Nerve Stimulation. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Author and Title** & **Population (Number, Gender, Age)** & **Methods (Protocol/Brain Area)** & **Outcomes/Results** \\ \hline [PERSON] et al. [16]: Anodal Bayesian analysis of the effect of transcranial direct current stimulation on experimental pain sensitivity in older adults with knee osteoarthritis: randomized sham-controlled pilot clinical study & 40 participants aged 50–70 years & 2 mA tDCS for 20 min; anode over C3/C4; cathode on the contralateral supraorbital area & Improved pain thresholds and reduced clinical pain symptoms \\ \hline [PERSON] et al. [17]: Efficacy of combining home-based transcranial direct current stimulation with mindfulness-based meditation for age 59.47 \(\pm\) 6.91 years & 120 participants; average age 59.47 \(\pm\) 6.91 years & Home-based tDCS and mindfulness meditation; anode over the primary motor cortex; cathode over the supraorbital region & Reduced experimental pain sensitivity \\ \hline [PERSON] [PERSON] et al. [18]: Longitudinal effect of transcranial direct current stimulation on knee osteoarthritis patients measured by functional infrared spectroscopy: a pilot study & 10 participants; average age 62.4 \(\pm\) 6.9 years & Self-treatment with 2 mA tDCS for 20 min; anode over the primary motor cortex & Increased cortical activity and reduced pain \\ \hline [PERSON] et al. [27]: The Effect of Transcranial Direct Current Stimulation on Inflammation in Older Adults With Knee Osteoarthritis: A Bayesian Residual Change Analysis & 40 participants aged 50–70 years & tDCS for 20 min daily for 5 days; anode over the primary motor cortex; cathode on the supraorbital area & Reduced inflammation markers \\ \hline [PERSON] et al. [28]: Randomized clinical trial comparing of transcranial direct current stimulation (tDCS) and transcutaneous electrical nerve stimulation (TENS) in knee osteoarthritis & 40 participants aged 51–71 years & tDCS vs. TENS; 2 mA for 20 min; electrodes over M1 and SO areas & tDCS showed a slight advantage in improving quality of life \\ \hline [PERSON] et al. [20]: Motor cortex transcranial direct current stimulation effects on knee osteoarthritis pain in elderly subjects with dysfunctional descending pain inhibitory system: A randomized controlled trial & 104 elderly subjects; mean age 73.9 \(\pm\) 8.01 years & 15 daily sessions of 2 mA tDCS; anode over M1 (C3/C4); cathode over SO & Significant pain relief \\ \hline [PERSON] et al. [29]: The effect of transcranial direct stimulation as an add-on treatment to conventional physical therapy on pain intensity and functional ability in individuals with knee osteoarthritis: A randomized controlled trial & & \\ \hline [PERSON] et al. [30]: Transcranial direct current stimulation for knee osteoarthritis: a single-blind randomized sham-controlled trial & 54 participants aged 30–70 years & tDCS combined with physical therapy; 2 mA for 20 min over 5 sessions & Reduced pain intensity and improved functional ability \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of studies on transcranial direct current stimulation (tDCS) for chronic knee pain.