Background Knee osteoarthritis (OA) has been associated with low serum 25 hydroxyvitamin D (25 OH D) levels. Studies that looked at the association of 25 OD D levels with OA progression have been sparse and gave confliction results.

Objectives To compare serum 25 OH D levels in medial femoro-tibial OA patients and controls, and to detect structural progression in patients with mild to moderate medial femoro-tibial OA in relation to baseline 25 OH D levels, by a one-year prospective MRI study.

Methods 20 pain free control subjects and 30 patients with medial femoro-tibial OA diagnosed according to the ACR criteria (all living in Cairo (Egypt) were included in the study. To be included, medial femoro-tibial OA patients had to be scored grade 2 or 3 according to the Kellgren-Lawrence classification on standing radiographs. Baseline serum levels of 25 OH D, and the “Benefiting from ultraviolet index” (BFUI) score (1) were determined. Serum PTH, alkaline phosphatase, calcium and phosphorus levels were also measured at baseline. OA patients were divided into 2 groups according to 25 OH D level, using a cutoff of 10 ng/mL. MRIs (Siemens Magneton, 1.5 Tesla) were performed at baseline and after 12 months. The Boston Leeds Osteoarthritis Knee Score (2) was determined at these two time points by an experienced rheumatologist, who was blinded to the 25 OH D status and MRI sequence. Patients were not supplemented with 25 OH D. The control group comprised 20 age, sex and BMI-matched healthy individuals who had their blood drawn for comparison with OA patient baseline values.

Results The mean values of 25 OH D were statistically lower in the OA patient group (8.64±6.42 ng/mL) than in matched controls (14.84±0.87 ng/mL, p=0.0295). An inverse correlation was observed between the levels of PTH and 25 OH D (r=0.72, p<0.01). BFUI scores overall correlated (r=0.75, p<0.01) with 25 OH D levels and were significantly lower (p<0.05) in OA patients, indicating lower sun exposure in the OA group.

No OA patient had a serum 25 OH level >20 ng/mL. 25 OH D levels were <10 ng/mL in 21 patients (vitamin D deficient, all females) and >10 ng/ml in 9 (vitamin D insufficient, 5 males, 4 females). MRI demonstrated significant (p<001) progression of the medial meniscal lesions from baseline to 1 year in the patients with 25 OH D levels <10 ng/ml. Among these 21 vitamin D deficient patients, three progressed from meniscus grade 0 to grade 1, one from grade 0 to grade 2, five from grade 1 to grade 2 and two from grade 1 or 2 to grade 3, whereas no meniscal progression was observed in the 9 insufficient OA patients.

Conclusions 25 OH D levels were low in our medial femoro-tibial OA patients and significantly decreased as compared to matched controls. Significant deterioration of the medial menisci was observed in OA patients with 25 OH D levels <10 ng/ml, suggesting that vitamin D deficiency may play a role in the progression of knee OA.

References

1. Atli T, et al. Arch Gerontol Geriatr 2005;40:53-60.

2. Hunter DJ et al. Ann Rheum Dis 2008;67:206-11

Disclosure of Interest None declared