Gladys L. Y. Cheing ^A1, Amy Y. Y. Tsui ^A1, Sing Kai Lo ^A1, Christina W. Y. Hui-Chan ^A1
A1 Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

DOI: 10.1080/16501970306116

Objective: This study examined the optimal stimulation duration of transcutaneous electrical nerve stimulation (TENS) for relieving osteoarthritic knee pain and the duration (as measured by half-life) of post-stimulation analgesia. Subjects: Thirty-eight patients received either: (i) 20 minutes (TENS 20 ); (ii) 40 minutes (TENS 40 ); (iii) 60 minutes (TENS 60 ) of TENS; or (iv) 60 minutes of placebo TENS (TENS PL ) 5 days a week for 2 weeks. Methods: A visual analogue scale recorded the magnitude and pain relief period for up to 10 hours after stimulation. Results: By Day 10 , a significantly greater cumulative reduction in the visual analogue scale scores was found in the TENS 40 (83. 40%) and TENS 60 (68. 37%) groups than in the TENS 20 (54. 59%) and TENS PL (6. 14%) groups (p 3 0. 000), such a group difference was maintained in the 2-week followup session (p 3 0. 000). In terms of the duration of post-stimulation analgesia period, the duration for the TENS 40 (256 minutes) and TENS 60 (258 minutes) groups was more prolonged than in the other 2 groups (TENS 20 = 168 minutes, TENS PL = 35 minutes) by Day 10 (p 3 0. 000). However, the TENS 40 group produced the longest pain relief period by the follow-up session. Conclusion: 40 minutes is the optimal treatment duration of TENS, in terms of both the magnitude (VAS scores) of pain reduction and the duration of post-stimulation analgesia for knee osetoarthritis.