…does it make any difference?
Inspired by Liu et al 2022.
TePs – tender pointskey to acronyms
OA – osteoarthritis
OAK – osteoarthritis of the knee
APs – acupuncture points
TrPs – trigger points
EA – electroacupuncture
This is a large clinical trial (n=666) from Chengdu that compares different acupuncture approaches to the treatment of OAK. It is not often we get the chance to look for differences between two real treatment approaches in a large RCT, so this is definitely worth highlighting.
222 patients with OAK were randomised to each group. Two groups received 12 acupuncture treatments over 4 weeks and the third group was offered free treatment at the end of the trial. I like this approach in acupuncture trials because it overcomes the argument that the measured effects are solely due to resentful demoralisation in the untreated group.
The patients were mostly women (~80%) with bilateral OAK (~80%). I don’t think the sex distribution is an issue, although there is some suggestion from one of the large German health economic evaluations that it may be less cost effective to treat men with OAK. But the predominance of bilateral OAK is relevant when you consider the methods (see below).
The basic tenet of the study was that it is better to treat local TePs (mostly tender APs) as opposed to APs that are not tender. This seems to be logical and one of the key principles of both TCM and WMA approaches.
Early in my acupuncture needling career, I noted that TePs seemed to be important from my own clinical audit of outcomes, but in those days, I was predominantly treating muscle pain. In muscle pain, a TeP is likely to be the site of a TrP, and I rapidly focussed more on TrPs. In OAK, TrPs are predominantly secondary phenomena, and I quickly gave up bothering to look for them, since EA to muscles around the knee seemed to work so well in terms of symptom relief.
Since the pathological features of OAK do not appear to alter dramatically with acupuncture treatment, it seems likely that the symptomatic improvement is mediated via inhibition of sensory amplification in the spinal cord (central sensitisation). This seems to be the most plausible way to explain how symptomatic relief can outlast the physiological effects of needling, since having turned down the amplification, it takes time and persistent nociceptive inputs to the cord to turn it up again.
In this theoretical scenario, what is the relevance of local TePs? Well, they could be sites of origin of nociceptive inputs to the cord, and acupuncture can be antinociceptive. The problem with this argument is that the antinociceptive effects of acupuncture are rather short-lived (minutes or hours). One could argue that needling may improve tissue oxygenation and reverse the peripheral sensitisation at a TeP, but we have already noted that there is no substantial change to the condition itself, so this becomes less plausible.
The points of interest around the knee were: Heding (EX-LE2); Neixiyan (EX-LE4); Dubi (ST35); Xuehai (SP10); Liangqiu (ST34); Yinlingquan (GB34); Zusanli (ST36); Weizhong (BL40); Yingu (KI10); Xiguan (LR7); Ququan (LR8); and Weiyang (BL39). An electronic von Frey detector was used to assess tenderness (pain threshold) at the points, and in one group the 5 most tender points were treated, and in the other group the 5 least tender points were treated. In bilateral OAK (the majority), only the worst side was tested, and the other side was treated with the same set of points in both groups: ST35; EX-LE4; GB34; ST36; and SP10.
I think it would have been better to just treat the worst side, although I doubt the results would have differed, since by using the same approach in both groups dilutes the physiological difference to a significant degree.
The acupuncture groups were highly significantly better than the waiting list control, but there was absolutely no difference between the treatment groups, apart from a minor difference in knee extension at one time point.
I could be accused of confirmation bias by highlighting this study, since it confirms my clinical decision some 25 years ago to not bother looking for TePs in OAK, but I am pretty sure I would have highlighted a study this size whatever the result.
It is worth noting that this is essentially a large negative explanatory trial plus a large positive pragmatic one rolled in together. Negative explanatory trials are relatively rare from China, so this naturally adds credibility to the results.
I guess I should point out that one of the German trials from the 00s on OAK was 3-armed and larger (n=1007). The sham arm of this trial involved superficial off-point segmental needling, so in effect we had two needling arms with over 300 patients in each. There was no significant difference between the two groups that received needling, so it was a long shot to think they could measure a difference with less statistical power in Chengdu.
1 Liu J, Li Y, Li L, et al. Effects of acupuncture at acupoints with lower versus higher pain threshold for knee osteoarthritis: a multicenter randomized controlled trial. Chin Med 2022;17:67. doi:10.1186/s13020-022-00626-3
2 Reinhold T, Witt CM, Jena S, et al. Quality of life and cost-effectiveness of acupuncture treatment in patients with osteoarthritis pain. Eur J Health Econ 2008;9:209–19. doi:10.1007/s10198-007-0062-5
3 Scharf H-P, Mansmann U, Streitberger K, et al. Acupuncture and knee osteoarthritis: a three-armed randomized trial. Ann Intern Med 2006;145:12–20. doi:10.7326/0003-4819-145-1-200607040-00005