Should i assume that if the findings of a hip joint x ray don't mention any type of arthritis being found, then there isn't any?

I wouldn't: assume anything. Sometimes, particularly as we age, a radiologist might consider a mild degree of degenerative arthritis to be "normal"and not mention it, or if the x-ray was performed for, say, trauma, only talk about acute findings that are significant in that setting. Call the radiologist, or your doc, and ask them to specifically address the question.