The Association Between Serum 25-hydroxy Vitamin D Level and Upper Leg Strength in Patients with Knee Osteoarthritis: Results of the Amsterdam Osteoarthritis Cohort

J Rheumatol. 2016 Jul;43(7):1400-5. doi: 10.3899/jrheum.150751. Epub 2016 May 15.


Objective: Vitamin D deficiency, which is common among elderly people, has been linked to muscle weakness. In patients with knee osteoarthritis (OA), the association between muscle strength and serum 25-hydroxy Vitamin D [25(OH)D] level has not been studied comprehensively. The aim of our study was to examine the association between serum 25(OH)D level and muscle strength in patients with knee OA.

Methods: Data of the Amsterdam Osteoarthritis cohort from 319 participants with knee OA were used in a cross-sectional study. Serum 25(OH)D level (nmol/l) was measured by a competitive electrochemiluminescence method. Muscle strength (nm/kg) of the upper leg was measured isokinetically. Univariable and multivariable linear regression analyses were used to calculate the association between serum 25(OH)D level and muscle strength.

Results: Serum 25(OH)D level was significantly associated with muscle strength (B = 0.036, 95% CI 0.017-0.054, p < 0.001), adjusted for season of blood collection. After adding body mass index (BMI) to the model, this association was no longer significant (B = 0.011, 95% CI -0.007 to 0.029, p = 0.214). Alcohol consumption, number of comorbidities, and sex were subsequently added and changed the model slightly. Without BMI, this model showed a significant association between serum 25(OH)D level and muscle strength (B = 0.029, 95% CI 0.014-0.043, p < 0.001).

Conclusion: The observed association between a low serum 25(OH)D level and muscle weakness in patients with knee OA is attenuated by BMI. Further studies are needed to explain the associations among Vitamin D level, muscle strength, and adiposity in patients with knee OA.


MeSH terms

  • Adult
  • Aged
  • Body Mass Index
  • Cross-Sectional Studies
  • Female
  • Humans
  • Male
  • Middle Aged
  • Muscle Strength / physiology*
  • Netherlands
  • Osteoarthritis, Knee / blood*
  • Osteoarthritis, Knee / physiopathology
  • Thigh / physiopathology*
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood


  • Vitamin D
  • 25-hydroxyvitamin D