<unk>  (AS) is a chronic inflammatory disease of the axial skeleton with variable involvement of other joints or even nonarticular structures
3x more common in males than females
Typically diagnosed in young adults between the ages of 20 and 30 yrs
Often associated with other autoimmune disorders
90% of people with AS express the HLA-B27 genotype
Uveitis is common extra-articular manifestation, seen in 30% of patients
Ankylosing spondylitis
Spine related
Osteoarthritis
Acute ligamentous injury
Rheumatoid arthritis
Acute muscle strain
Reactive arthritis
Disk herniation 