BACKGROUND AND OBJECTIVE: Transcutaneous electrical nerve stimulation (TENS) is commonly used for treatment of pain; however the effects on a variety of pain and function measures is unclear. The purpose of the current study was to determine the effect of high (HF) and low (LF) frequency TENS, on a variety of outcome measures: resting pain, movement-evoked pain, and pain sensitivity in subjects with osteoarthritis of the knee. SUBJECTS: 75 subjects with knee osteoarthritis (31 to 94 years, M = 29, F = 46) were assessed. METHODS: Subjects were randomly assigned to receive HF-TENS (100 Hz) (n = 25), LF-TENS (4 Hz) (n = 25) or placebo (P) TENS (n = 25; pulse duration = 100msec; intensity = 10% below motor threshold). The following measures were assessed before and after a single TENS treatment: cutaneous mechanical pain threshold (CMPT), pressure pain threshold (PPT), heat pain threshold (HPT), heat temporal summation (HTS), Timed Up and Go (TUG) test, and pain intensity at rest and during the TUG test. A linear mixed model ANOVA compared differences before and after TENS, and between groups (HF, LF, and P). RESULTS: When compared to P-TENS, HF-TENS and LF-TENS increased PPT at the knee; HF-TENS also increased PPT over the anterior tibialis muscle. There was no effect on CMPT, HPT, or HTS. HF-, LF- and P-TENS significantly reduced the pain at rest and during the TUG test. CONCLUSION: When compared to P-TENS, HF- and LF-TENS reduced pressure pain sensitivity in knee OA subjects -- P-TENS had no significant effect on PPT. Cutaneous pain measures were unaffected by TENS. Subjective pain ratings at rest and during movement were similarly reduced by active and placebo TENS suggesting a strong placebo component to the effect of TENS.

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