Can Osteoarthritis Cause Other Problems?

My wife is 52. She has severe knee pain, diagnosed as OsteoArthritis. Has gone through Posture correcting shoe, pain killers (paracitamol, diclofanac, tramadol, glaucosamine, diacerin and some others.Recently she was advised blood test where abnormalities were Vitamin D3 level was "less than 4" inplace of ~30, ESR was at one time 70 but came down to 40 after a week. Can she be suffering from some other desease? What other test shall we go for?