The appropriate form and dosing of vitamin K to benefit relevant outcomes in knee osteoarthritis (OA) are not known. In intervention studies for conditions other than knee OA (e.g., prevention of cardiovascular disease), the most commonly used forms and doses include phylloquinone (vitamin K1; 1000µg or 500µg daily) or menaquinone-7 (MK-7 or vitamin K2; 300µg daily). However, whether these doses are adequate to increase vitamin K to levels that ameliorate risk of adverse OA outcomes is not known. Furthermore, although some studies suggest enhanced bioavailability of MK-7 over vitamin K1, as well as extra-hepatic effects, whether this is relevant for an older population with knee OA is not known, The overall goal of this pilot randomized clinical trial (RCT) is to test different subtypes and doses of vitamin K supplementation in older adults with knee OA and to measure changes in relevant biochemical measures.