I am a 24 year old female. my lower back is stiff & hurts & my knees always make a crackling noise . could this be arthritis?

24 yo LBP: It could be arthritis, inflammatory, as osteo is rare at your age unless you engaged in significant sports or gymnastics./ ballet or repetitive heavy work, or had MVA. Would consider LS spine xray r/o spine, SI joint disease, blood work including CRP, ANA HLA B27, discuss food intolerances , bowel issues as that can be a factor, try motrin if not allergic, rarely may be ovarian. f/u/ w/ doc