Today, Knee osteoarthritis (OA) is assumed to be highly prevalent as due to recent increases in life expectancy and body mass index (BMI), but this assumption has not been tested applying the long-term historical or evolutionary data.

According to many epidemiological studies, preliminary evidence supporting the potential use of vitamin D for OA treatment has been supplemented. Greater knee pain was concerned with lower serum levels of 25-(OH)D and higher frequency of radiographic OA. Also, higher dietary consumption of Vitamin C leads to decrease in subchondral bone marrow lesions (which may be concerned with the pathogenesis of OA) in the knee evaluated by MRI. Both vitamins C and D are considered to be related to decreasing pain and increasing function, but these relationships are not convincing enough.

Therefore, Hung M et al. conducted cross-sectional study to explore that what relationships supplemental and dietary intake of Vitamins C and D have on pain severity and physical function in knee OA patients. The data was collected from the Osteoarthritis Initiative, and the regression analyses were performed. This helped to examine the relationships between Vitamins C and D, pain, and function. The dietary Vitamin D and Vitamin C were categorized into >90th, 50th-90th, and <50th percentile. The high percentile groups for supplemental Vitamin D and Vitamin C were classified into >85th percentile and >90th percentile. 

The results of the study depicted the 90th/85th percentile levels of dietary and supplemental vitamin D to be positively connected with pain (β = 0.180; p = 0.028) and inversely linked to physical function (β = -0.150, p = 0.028). No statistical difference was observed with daily consumption of vitamin C.

Thus, supplementary vitamin D was strongly related with an alleviated disability for knee OA patients. The unexpected verdict that dietary vitamin D is related to greater knee pain gives way to future study.