The study of the placebo effect is key to elucidate the ‘real effect’ of conservative interventions for plantar fasciitis. The aim of this meta-analysis was to quantify the impact of placebo in the different conservative treatments of plantar fasciitis.

A systematic literature review was performed on double-blind placebo-controlled trials (RCTs) according to PRISMA guidelines on PubMed, Embase, and Web of Science. The meta-analysis primary outcome was the 0–10 pain variation after placebo treatments analyzed at 1 week, 1, 3, 6, and 12 months. The risk of bias was assessed using the RoB 2.0 tool, while the overall quality of evidence was graded according to the GRADE guidelines.

The placebo effect for conservative treatments was studied in 42 double-blind RCTs on 1724 patients. The meta-analysis of VAS pain showed a statistically significant improvement after placebo administration of 2.13/10 points (P < 0.001), being highest at 12 months with 2.79/10 points (P < 0.001). The improvement of the placebo groups was higher in the extracorporeal shock wave therapy studies compared to the injection studies (2.59 vs 1.78; P = 0.05). Eight studies had a low risk of bias, 23 studies had ‘some concerns,’ and 4 studies had a high risk of bias. The GRADE evaluation showed an overall high quality of evidence.

This systematic review and meta-analysis demonstrated that the placebo effect represents an important component of all conservative approaches to treat plantar fasciitis. This effect is statistically and clinically significant, increases over time, and depends on the type of conservative treatment applied to address plantar fasciitis.

Intra-articular corticosteroid (CS) injections for knee osteoarthritis (OA) management are endorsed by several scientific societies, while the use of hyaluronic acid (HA) and platelet-rich plasma (PRP) is more controversial. Aim of the study was to quantify and compare the clinical effectiveness of CS injections with respect to HA and PRP in patients with knee OA.

The search was conducted on PubMed, Cochrane, and Web of Science following the PRISMA guidelines. Randomized controlled trials (RCTs) on the comparison of CS injections and HA or PRP injections for the treatment of knee OA were included. The minimal clinically important difference (MCID) was used to interpret the clinical relevance of the improvements at different follow-ups up to 12 months. The study quality was assessed using the Cochrane RoB-2 tool and the GRADE guidelines.

Thirty-five RCTs were included (3348 patients). The meta-analysis comparing CS and HA revealed no difference in terms of WOMAC improvement, while HA showed superior VAS pain improvement at long-term follow-up (P = 0.011), without reaching the MCID. PRP offered a superior WOMAC improvement compared to CS at short- (P = 0.002), mid- (P < 0.001, exceeding the MCID), and long-term (P < 0.001, exceeding the MCID) follow-ups. PRP offered a superior VAS improvement at mid- (P < 0.001, exceeding the MCID) and long-term (P = 0.023) follow-ups.

CS injections for knee OA offer similar results to HA and PRP only at short term, while there is an overall superiority of PRP at longer follow-ups. This difference is not only statistically significant but also clinically relevant in favour of PRP.