Restorative Effect of Vitamin D Deficiency on Knee Pain and Quadriceps Muscle Strength in Knee Osteoarthritis

Both vitamin D deficiency and quadriceps muscle weakness are associated with knee osteoarthritis (KOA) and pain. The aim of this study was to determine the restorative effect of vitamin D deficiency on pain and quadriceps muscle strength in knee osteoarthritis. Patients with KOA aged ≥30 years, the presence of knee pain for at least one month or longer and serum 25-hydroxyvitamin (25-OHD) deficiencies were recruited in the study. Participants with KOA compatible with Kellgren-Lawrence grade 4, joint instability, and effusion, history of surgery or inflammatory arthropathies were excluded. Serum 25-OHD was assessed by ELISA method and concentrations<20 ng/ml was considered deficiency. Quadriceps muscle strength was measured by dynamometry method and intensity of knee pain by Western Ontario and McMaster University Osteoarthritis index scored by Likert scale and visual analog scale. All participants received 50.000 IU oral cholecalciferol weekly for at least two months. The influence of raising serum 25-OHD on quadriceps muscle strength and pain was assessed by calculation of mean changes from baseline at the end of the treatment period using paired t-test. A total of 67 patients with mean age of 50±6.6 years of age were treated for 2 months. Serum 25-OHD reached to sufficient levels in all except one patient. At the end of the study period, serum 25-OHD and quadriceps muscle strength increased significantly as compared with baseline (P=0.007 and P=0.002, respectively), whereas knee pain decreased significantly based on Western Ontario and McMaster University Osteoarthritis index (P=0.001)as well as visual analogue scale scores (P=0.001). These findings indicated that correction of vitamin D deficiency in patients with KOA exerts a significant favorable effect on quadriceps muscle strength and knee pain.