Pain relief experienced by patients with osteoarthritis (OA) of the knee may be attributed to contextual effect, especially in those patients receiving acupuncture or electrotherapies, according to a study published in Osteoarthritis and Cartilage.
This was the first study to quantify the contextual effect of nonpharmacologic, nonsurgical treatments (NPNS) on knee OA. Previous studies have examined the placebo effect, “an important component of the contextual effect,” the researchers said. “Contextual effect may include the placebo effect, changes attributable to natural history, and effects of cotherapies. These factors can influence therapeutic outcomes substantially.”
NPNS treatments, including acupuncture, laser, ultrasound, and transcutaneous electrical nerve stimulation (TENS), present low-risk, low-cost options for treatment of OA. “If such a large proportion of pain treatment effect in NPNS treatments of knee OA is indeed contextual, then finding ways to ethically bolster contextual effect may present an opportunity to enhance clinical care,” reported the researchers.
The research team searched MEDLINE, Embase, Web of Science, CINAHL, and Cochrane Central to identify knee OA trials. Studies were included if they reported on both active and placebo arms, enrolled individuals with knee OA who had not received a total knee replacement, involved active treatment modalities, reported a pain outcome, included a follow-up assessment, and reported an improvement of pain at baseline. Studies including ultrasound, TENS, and laser were combined under the term total energy modality (TEM).
The final analysis consisted of 25 total acupuncture and TEM studies; only 1 study included exercise therapy and therefore was excluded. The age of patients were similar between the 2 groups: the mean age ranged from 57 to 71 years for the acupuncture studies and from 53 to 69 for TEM studies. All studies included a follow-up assessment of knee pain at 28 to 91 days after baseline measurement.
“We calculated the proportion [of pain relief] attributable to contextual effect [PCE] for each study by dividing the mean improvement in pain – the improvement in average pain between baseline and follow-up measurements – of the placebo group by the mean improvement in pain of the active group,” the researchers said. Pooled analysis found that contextual effects accounted for approximately 61% of the pain relief experienced by patients receiving active treatment in the acupuncture studies; and 69% of the total treatment effect in TEM studies.
After excluding 4 acupuncture studies with cotherapies, the pooled PCE results increased to 73%; in contrast, the exclusion of 6 TEM studies with cotherapies reduced the PCE results to 44%.
“This systematic review shows that factors other than the direct effect of an active treatment may play an important role in the analgesic effects experienced by knee OA patients receiving acupuncture or TEM,” concluded the authors. “Further research is needed to determine how contextual effects vary across treatment approaches – including exercise – and outcome measures, and how to harness the benefits of contextual effects in ways that align with patient goals.”
Chen AT, Shrestha S, Collins JE, Sullivan JK, Losina E, Katz JN. Estimating contextual effect in nonpharmacological therapies for pain in knee osteoarthritis: a systematic analytic review [published online May 13, 2020]. Osteoarthritis Cartilage. doi:10.1016/j.joca.2020.05.007.