Do vitamin D levels affect the clinical prognoses of patients with knee osteoarthritis?

OBJECTIVE: Although vitamin D deficiency has been associated with osteoporosis, as well as fractures, in elderly men and women, the role of vitamin D deficiency in the pathogenesis of osteoarthritis (OA) remains controversial. In this study, we aimed to investigate the effects of vitamin D deficiency on the functional status and disease prognosis of patients with knee osteoarthritis. PATIENTS AND METHODS: Our study comprised 100 patients that met the American College of Rheumatology criteria for a diagnosis of knee osteoarthritis. Each patient underwent knee radiography, the results of which were graded according to Kellgren and Lawrence radiographic grading scale; those that met the diagnostic criteria were included in the study. The visual analog scale (VAS), Nottingham Health Profile (NHP), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Lequesne Knee Osteoarthritis Index were used to assess patients' pain, function and quality of life. Complete blood counts, sedimentation rates and serum C-reactive protein, rheumatoid factor, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, sodium, potassium, calcium, phosphorus, parathyroid and thyroid hormone levels were routinely recorded for each patient. Vitamin D levels were analyzed in winter (between November and February) using high performance liquid chromatography. RESULTS: Patients were divided into two groups, Group 1 and Group 2, according to the presence or absence of vitamin D deficiency. The groups did not differ significantly in terms of age, disease duration, sex distribution, presence of osteoporosis or radiographic stage of knee osteoarthritis (p = 0.793, 0.092, 0.250, 0.835 and 0.257, respectively). However, the NHP pain, physical activity, fatigue, social isolation, and emotional reactions subsets, WOMAC pain and physical function subsets and total score, Lequesne knee osteoarthritis index, and patient/physician VAS scores were significantly higher in Group 1 than in Group 2 (p < 0.05). CONCLUSIONS: Our study therefore suggests that vitamin D deficiency exacerbates pain, dysfunction and a poorer quality of life in patients with knee osteoarthritis. Further longer-term studies are needed to investigate the effects of vitamin D deficiency on OA-related symptoms.