see also:

• arthritis - clinical patterns

• ankylosing spondylitis
• other seronegative spondyloarthopathies:
  • psoriatic
  • Reiter's
  • JCA
  • inflammatory bowel disease (IBD)
• infection - septic / tuberculosis (TB) / brucellosis
• recurrent polyserositis (familial Mediterranean fever)
• ochronosis (alkaptonuria)
• consider also osteoporotic sacral insufficiency fracture (SIF)