Background: This study is primarily aimed to determine whether transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC) treatments have any effect on central sensitization (CS) in patients with knee osteoarthritis (OA) and to investigate which treatment is more effective.
Methods: In this randomized controlled trial, 80 patients were randomized into four treatment groups: TENS, Plasebo-TENS, IFC, and Plasebo-IFC. All interventions were applied 5 times a week for 2 weeks. Primary outcome was pressure pain threshold (PPT), which is accepted as the objective indicator of CS, at the painful knee and at the shoulder as a painless distant point. Other outcome measures were the visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index, Timed Up and Go Test, pain catastrophizing scale, Beck Depression Inventory, and Tampa Scale of Kinesiophobia.
Results: All assessment parameters were improved, without a significant difference among the groups except PPT. PPT scores were significantly improved in TENS and IFC groups when compared with the sham groups at 2 weeks and 3 months. In addition, this improvement was even more pronounced in the TENS group. Multivariable logistic regression analysis showed that the patient’s inclusion in the TENS group, an initial high PPT, and an initial low VAS score were independent risk factors for improvement in the PPT.
Conclusions: This study shows that TENS and IFC reduced pain sensitivity as compared to placebo groups in patients with knee OA. This effect was more pronounced in the TENS group.

Keywords: Catastrophization, Central Nervous System Sensitization, Electric Stimulation Therapy, Hyperalgesia, Kinesiophobia, Osteoarthritis, Knee, Pain Management, Pain Threshold, Physical Therapy Modalities, Transcutaneous Electric Nerve Stimulation.