Can't fully extend elbows

I have pretty bad mobility by all accounts, but my elbows seem to have particularly bad mobility. I can't extend/straighten them all the way, and I have never been able to do so. So for instance if I ever try to do a handstand I won't be able to lock them out which will suck. It doesn't feel like any muscle tightness is keeping it from extending, it just feels like the joint itself is locked and won't allow for full ROM. Anybody else in the same boat, or know what the issue is?