My vitiman D showed low on my last lab work everything else was fine. My Dr had me take a Vitiman over the counter. Lately my knee is bothering me Should I be taking more vitiman D? It’s very stiff in the AM n hard to walk normally. Other days doesn’t hurt as bad. My bone by my neck cracks when I move a certsin ways! Is this caused by low D or could it be arthritis?? Iam 71.and never had bone issues before. Should I be taking a RX for this or keep up with the vitiman D over the counter. It’s 170 units I take for vitiman D. Thank you n thank you for your last answer to me!!