Can someone let me know if this is normal.

I have a Kona MTB with Kona bars and stem (haven't changed since I bought the bike brand new about 2 years ago).

For the last long while (maybe a year or maybe since I bought it) I have heard a creak that sounds like it might be the bar in the stem. I am wondering if this is normal or should I worry about it. It only creaks when I am really pulling on the bar (like taking off or climbing, etc.) It doesn't sound like it's about to break or anything like that, it sounds very solid (which is why I haven't worried about it).

Can anyone tell me if I need to replace anything, adjust anything or is it normal to hear such creaks.