Background <p>Tendinopathy is a common musculoskeletal condition associated with persistent pain and functional limitation. Although vitamin D deficiency has been widely implicated in musculoskeletal disorders, its association with clinical outcomes in tendinopathy remains incompletely understood. This study investigated the association between serum vitamin D levels, clinical severity of tendinopathy, and the effects of vitamin D supplementation.</p> Methods <p>This retrospective observational study included 350 patients with tendinopathy treated at a tertiary referral center between 2023 and 2025. Patients were classified into a vitamin D supplementation group (<i>n</i> = 221), receiving 50,000&#xa0;IU weekly for 4&#xa0;weeks followed by 2000&#xa0;IU daily for 8&#xa0;weeks, and a nonsupplemented group (<i>n</i> = 129). Pain intensity (VAS), functional status (0–100 scale), disease duration, chronicity, and ultrasonographic inflammation severity were evaluated.</p> Results <p>Patients with serum vitamin D levels below 20&#xa0;ng/mL exhibited significantly higher pain scores (7.3 ± 1.2 vs. 5.7 ± 1.3, <i>p</i> &lt; 0.001), longer disease duration (8.2 vs. 4.1&#xa0;months, <i>p</i> &lt; 0.001), and a higher prevalence of chronic tendinopathy (79.6% vs. 24.0%, <i>p</i> &lt; 0.001). Following supplementation, serum vitamin D levels increased from 14.2 to 38.4&#xa0;ng/mL (<i>p</i> &lt; 0.001), accompanied by significant reductions in pain and improvements in functional status compared with the nonsupplemented group (<i>p</i> &lt; 0.001). Severe vitamin D deficiency (&lt; 10&#xa0;ng/mL) was independently associated with a sevenfold increased likelihood of severe and chronic tendinopathy (OR: 7.2, <i>p</i> &lt; 0.001).</p> Conclusions <p>Vitamin D deficiency is strongly associated with greater clinical severity and chronicity of tendinopathy. Vitamin D supplementation is associated with meaningful improvements in pain and functional outcomes, suggesting that vitamin D status represents a clinically relevant and potentially modifiable factor in tendinopathy management.</p> <p><i>Clinical trial registration</i> Clinical trial number: not applicable. This study was a retrospective observational study and was, therefore, not registered as a clinical trial.</p>

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Association of vitamin D deficiency and supplementation with clinical outcomes in multi-tendon chronic tendinopathy: a retrospective clinical study

  • Volkan Kizilkaya,
  • Sefa Erdem Karapinar,
  • Namik Kemal Kilinccioglu,
  • Mehmet Melih Asoglu,
  • Mustafa Cukurlu,
  • Fatih Enzin,
  • Ali Levent

摘要

Background

Tendinopathy is a common musculoskeletal condition associated with persistent pain and functional limitation. Although vitamin D deficiency has been widely implicated in musculoskeletal disorders, its association with clinical outcomes in tendinopathy remains incompletely understood. This study investigated the association between serum vitamin D levels, clinical severity of tendinopathy, and the effects of vitamin D supplementation.

Methods

This retrospective observational study included 350 patients with tendinopathy treated at a tertiary referral center between 2023 and 2025. Patients were classified into a vitamin D supplementation group (n = 221), receiving 50,000 IU weekly for 4 weeks followed by 2000 IU daily for 8 weeks, and a nonsupplemented group (n = 129). Pain intensity (VAS), functional status (0–100 scale), disease duration, chronicity, and ultrasonographic inflammation severity were evaluated.

Results

Patients with serum vitamin D levels below 20 ng/mL exhibited significantly higher pain scores (7.3 ± 1.2 vs. 5.7 ± 1.3, p < 0.001), longer disease duration (8.2 vs. 4.1 months, p < 0.001), and a higher prevalence of chronic tendinopathy (79.6% vs. 24.0%, p < 0.001). Following supplementation, serum vitamin D levels increased from 14.2 to 38.4 ng/mL (p < 0.001), accompanied by significant reductions in pain and improvements in functional status compared with the nonsupplemented group (p < 0.001). Severe vitamin D deficiency (< 10 ng/mL) was independently associated with a sevenfold increased likelihood of severe and chronic tendinopathy (OR: 7.2, p < 0.001).

Conclusions

Vitamin D deficiency is strongly associated with greater clinical severity and chronicity of tendinopathy. Vitamin D supplementation is associated with meaningful improvements in pain and functional outcomes, suggesting that vitamin D status represents a clinically relevant and potentially modifiable factor in tendinopathy management.

Clinical trial registration Clinical trial number: not applicable. This study was a retrospective observational study and was, therefore, not registered as a clinical trial.