EA for guinea pig OAK

Inspired by Spittler et al 2021,[1] Lam et al 2021,[2] and Ko et al 2021.[3]

A Hartley guinea pig – a laboratory breed.

EA – electroacupuncture
MA – manual acupuncture
OAK – osteoarthritis of the knee
RCT – randomised controlled trial
SR – systematic review
IF – impact factor
C3 – complement component 3 (serum C3 rises in inflammation)
VAS – visual analogue scale
TKR – total knee replacement

key to acronyms

I have chosen three papers published in June to highlight this week. They are quite different papers, but all linked by OAK. We have one laboratory study, one RCT and one SR. I have just noticed as well that the journals all have Medicine in their titles: Acupuncture in Medicine (IF 2.129); American Journal of Medicine (IF 4.529); and Pain Medicine (IF 2.513).

We start with an animal model of OAK in guinea pigs. But it is not really a model, since these Hartley guinea pigs naturally get moderate to advanced OA by the time they are 12 months old, when this experiment was performed on 10 of them. They were randomised to receive EA under anaesthesia or anaesthesia without EA.

EA was performed across 3 pairs of 0.16x30mm Seirin needles placed in the lumbosacral region, hip, and forelimb. MA was performed with 0.14x15mm Seirin needles at the same time to 7 further points including 3 around the knee. The animals were lying on one side, so the treatment was performed for 5 minutes on each side. The animals received 3 sessions per week for 3 weeks without complication.

EA treated animals were faster and took bigger strides

The treated animals were faster on their feet and travelled further than controls in open field monitoring, and their stride length was greater on treadmill gait analysis.

Histology and serum inflammatory markers were similar in the groups, although there was a trend towards reduced C3 in the EA group. Gene expression was measured in knee cartilage and in muscle at ST36. Genes involved in cartilage structure and antioxidant activity were upregulated in the EA group.

The RCT comes from Hong Kong and compared superficial acupuncture with a non-penetrating sham in patients (n=86) with OAK. At first this sounded to me like a comparison between 2 forms of sham acupuncture, but when I delved a bit deeper, I found that the style of superficial acupuncture was called sinew acupuncture, and it is not at all like the sort of superficial acupuncture used as a sham technique.

sinew acupuncture

I tracked down the protocol for the trial to confirm the method used.[4] It involves insertion of needles at 10 degrees to the skin surface along the direction of the pain and the meridian sinew. Insertion was performed with 0.30x40mm needles at 10–20mm from the tender points around the knee. My impression is that the needle is inserted fully, probably into muscle despite the shallow angle, but then immediately withdrawn and inserted smoothly 10–20mm under the skin, where it is retained. 5 to 8 points were treated, and each needle position was checked for comfort by extension and flexion of the knee, before they were covered with bandages. The patients were then asked to walk around for 10 minutes and perform step ups on an 18cm high step 12 times per knee. The needles were then removed but the bandages replaced to maintain blinding. The sham technique involved placing the needles onto the skin without insertion before being covered with bandages.

10 sessions of acupuncture were performed over 4 weeks, and both groups improved with a reduction in VAS pain of 30.8 in the acupuncture group and 26.7 in the sham group from a baseline of just over 70. There were no statistically significant differences between the groups. There are several possible explanations, but the lack of statistical power is probably one of the more important factors.

I think this form of acupuncture is designed for immediate pain relief, and there are similarities with movement acupuncture and Fu’s subcutaneous needling. The latter uses a specially designed needle with a plastic sheath reminiscent of a large bore cannula but without any bore. It is like a modern version of wrist ankle acupuncture, where the needles are inserted superficially under the skin and retained for perhaps 30 minutes.

dramatic and convincing in the short term

It could be that the effects of such interventions are dramatic and convincing to clinicians in the short term, but this RCT did not measure immediate effects, and the lack of deep somatic nerve stimulation may mean that the longer term effects via descending inhibitory systems is not as effectively achieved as say with strong intramuscular EA,[5] as highlighted previously on the blog: Strong EA and CPM on OAK.

 Finally, we come to the SR, which claims to examine the effectiveness of acupuncture as an analgesic following TKR. I reviewed a similar SR on the blog in February 2021: Acupuncture and arthroplasty.[6] The latter had a slightly broader scope focussing on rehabilitation rather than just analgesia, but several of the trials included are the same.

The SR included 7 RCTs with 891 TKR patients, and the previous SR included 9 RCTs with 671 patients. Since all but one of the 7 RCTs compared acupuncture with a sham, the results indicate efficacy more than effectiveness. The study that did not use a sham was an A+B vs B design, and so had a much bigger effect size than the sham controlled trials and was an outlier in the meta-analyses. I was surprised the authors did not exclude this one to confirm pure efficacy and to reduce the clinical and statistical heterogeneity.


1          Spittler AP, Afzali MF, Martinez RB, et al. Evaluation of electroacupuncture for symptom modification in a rodent model of spontaneous osteoarthritis. Acupunct Med Published Online First: 9 June 2021. doi:10.1177/09645284211020755

2          Lam WC, Au KY, Qin Z, et al. Superficial needling acupuncture versus sham acupuncture for knee osteoarthritis: a randomized controlled trial. Am J Med Published Online First: 11 June 2021. doi:10.1016/j.amjmed.2021.05.002

3          Ko HF, Chen C-H, Dong K-R, et al. Effects of Acupuncture on Postoperative Pain after Total Knee Replacement: Systematic Literature Review and Meta-Analysis. Pain Med Published Online First: 21 June 2021. doi:10.1093/pm/pnab201

4          Au KY, Chen H, Lam WC, et al. Sinew acupuncture for knee osteoarthritis: study protocol for a randomized sham-controlled trial. BMC Complement Altern Med 2018;18:133. doi:10.1186/s12906-018-2195-8

5          Lv Z, Shen L, Zhu B, et al. Effects of intensity of electroacupuncture on chronic pain in patients with knee osteoarthritis: a randomized controlled trial. Arthritis Res Ther 2019;21:120. doi:10.1186/s13075-019-1899-6

6          Chen Z, Shen Z, Ye X, et al. Acupuncture for Rehabilitation After Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Front Med 2021;7. doi:10.3389/fmed.2020.602564

Declaration of interests MC