Based on the results of the studies by Law et. al (2004) and Cheing et. al (2002), the use of TENS results in statistically significant improvements in pain across sessions, and based on the results by Law et. al (2004) the improvements achieve a clinically important difference in pain relief within treatment groups after 10 sessions and at the 2 week follow up. When comparing the pain outcomes to a placebo TENS intervention, the results from either study do not strongly suggest that TENS is more effective than placebo TENS treatment. If TENS treatment is used, however, it is more likely that the effects on pain relief are seen after 10 sessions and last up to 2-4 weeks after the end of TENS treatment. The most effective TENS parameters determined from both studies are 2 Hz and a pulse width of 576 μs or 100 Hz and a pulse width of 200 μs. The main threats to internal validity in both studies are the lack of blinding of therapists, a study loss of 6%, and small sample sizes. The first two threats are minor, but larger sample sizes would improve the generalizability of the outcomes. The main cost is time and financial cost of treatment, but the treatment is within reason to be covered by insurance. The recommendation from both studies is that as long as there are no contraindications to TENS and other pain relief methods have not worked for patients with knee OA, there is no harm in a TENS treatment trial with patient agreement to the TENS treatment as well as the time and financial cost associated with treatment using one of the 2 sets of TENS parameters mentioned above for 10 sessions with possible clinically important improvement in long term pain.
Is TENS effective in reducing short term and/or long term knee pain as measured by the visual analogue scale (VAS) in patients with knee OA?
The patient who led me to pursue this question is a 50 year old female with diagnoses including right knee OA, sepsis, deep vein thrombosis and gout. Her previous medical history includes hypertension, renal insufficiency, gastro esophageal reflux disease and heart transplant. Medical treatment to date for the OA has included medications and ice pack for pain relief. Problems identified include limited functional mobility and endurance secondary to knee pain, and general lower extremity weakness.
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