VDR and osteoarthritis, knee: However, data from Middle Eastern and Kurdish populations remain limited.<h4>Objective</h4>This study aimed to evaluate the association between serum vitamin D status and four common VDR gene polymorphisms (FokI, ApaI, TaqI, and BsmI) in Kurdish adults with knee osteoarthritis.<h4>Methods</h4>A hospital-based case-control study was conducted, including 100 OA patients and 100 healthy controls recruited in Erbil, Iraq.