Global prevalence of vitamin D deficiency among patients with knee osteoarthritis: A systematic review and meta-analysis.

Background: Low serum 25-hydroxyvitamin D (25[OH]D) levels affect bone remodeling, contributing to the development and progression of knee osteoarthritis (OA). Aim: This meta-analysis aimed to estimate the prevalence of vitamin D deficiency in patients with knee OA. Methods: A systematic search was conducted in Europe PMC, Google Scholar, Scopus, Scilit, and Web of Science for studies published until 8 August 2024 that reported the prevalence and contributing factors of hypovitaminosis D in knee OA patients. Study quality was assessed using the Newcastle-Ottawa Scale. A random-effect meta-analysis with Freeman-Tukey double arcsine transformation estimated the pooled prevalence of vitamin D deficiency. Results: Out of 1695 records identified, 26 studies (n = 4248 patients) met the inclusion criteria. The pooled prevalence of vitamin D deficiency was 56.72% (95% CI: 46.93-66.25). No significant difference was observed across publication periods of 2015-2019 (p = 0.465) and 2020-2024 (p = 0.407). Patients with an average body mass index (BMI) ≥28 kg/m² had a higher prevalence (65.62%, 95% CI: 49.23-80.32) compared to those with BMI <28 kg/m² (37.63%, 95% CI: 24.72-51.48). The prevalence was significantly higher in European countries (65.92%, 95% CI: 47.17-82.43) than in the USA (p = 0.046). In Asia, the Middle East, and North Africa, prevalences were 60.96% (95% CI: 42.32-78.08) and 63.11% (95% CI: 43.8-80.47), respectively. Conclusion: Over half of knee OA patients had vitamin D deficiency, with higher prevalence in Europe and among individuals with obesity. Targeted screening for 25(OH)D levels in knee OA patients is recommended.