Efficacy and Safety of Intra-Articular Botulinum Toxin A Injection for Knee Osteoarthritis: A Systematic Review, Meta-Analysis, and Meta-Regression of Clinical Trials

Botulinum toxin A has the potential to be used for analgesia because of its anti-inflammatory effect. The utility of intra-articular injections of botulinum toxin A for knee osteoarthritis remains unclear. The aim of this study was to analyze the utility of such injections in knees with osteoarthritis. METHODS: We conducted a literature search of 4 databases (Scopus, PubMed, ClinicalTrials.gov, and Europe PMC) up to September 10, 2022, using formulated keywords. Articles were included in the study if they had data on botulinum toxin A injection compared with the control group in patients with osteoarthritis of the knee. Results were summarized using the standardized mean difference (SMD) and accompanying 95% confidence interval (CI). RESULTS: Pooled analysis of data from 6 trials involving 446 patients with knee osteoarthritis revealed that, compared with placebo, intra-articular injection of botulinum toxin A was associated with greater reductions in early visual analog scale (VAS) pain (SMD, −0.63 [95% CI, −1.08 to −0.18], p = 0.007, I(2) = 79%), late VAS pain (SMD, −0.57 [95% CI, −1.07 to −0.08], p = 0.02, I(2) = 81%), early Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (SMD, −0.84 [95% CI, −1.61 to −0.06], p = 0.03, I(2) = 90%), and late WOMAC (SMD, −1.12 [95% CI, −1.91 to −0.32], p = 0.006, I(2) = 93%) scores from baseline in patients with knee osteoarthritis. CONCLUSIONS: Intra-articular injection of botulinum toxin A may offer benefits in reducing pain and improving function in patients with knee osteoarthritis, with a relatively good safety profile. Larger randomized trials are warranted to confirm the results of our study. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.