Teen with chronic joint pain

I have an 18 year old daughter who has been suffering from joint pain for about 3 and a half years now.  Her pain started in one knee and gradually over time has extended to her other knee, hips, ankles, shoulders, and lower back.
She has seen many doctors, has had x-rays, MRIs, and one arthroscopy surgery on her knee.  She has soft cartilage in her knees.  She tried taking glucosamine but found no relief after 6 months so she stopped taking it.
She cries to me almost every night.  
We are beside ourselves.  What will she be like in her 40s,50s,etc?
Does anyone have any suggestions as to what it might be?

[kirb_dude1]

has she been tested for ankylosing spondylitis? rheumatoid arthritis? does she ever pop her own back? what is her weight, height, race? is there any inflamation (inflammation) on joints in x-rays, any spinal MRI? spinal x-ray? what knee was her arthroscopy on? where is the back pain centralized? where are the knee pains(what part of knee)?does she experience pain in the chest at all(non-cardiac)? is there any sign of inflamation (inflammation) on her knuckles? if it is ankylosing spondylitis she will live in pain for the rest of her life as her spine eventually becomes fused and almost unable to move, this will induce extreme pressure on the nerves coming out of the spine causing reffered pain all over the body... however we cant be sure...more info please?

[justliveyalife]

Does she have any other symptoms...or just the joint pain? and...are the joints swollen and red...or just hurting?