Muscular strain
Osteoarthritis – Hip osteoarthritis
Herniated disk
Spinal stenosis
Cauda equina tumor
Sciatica
Sacroiliitis, eg, ankylosing spondylitis
Idiopathic (sprain, strain)
Spondylosis (disk, annulus, facet)
Compression fracture – e.g. caused by osteoporosis, multiple myeloma
Traumatic fracture
Spondylolisthesis
Kyphosis,
Scoliosis,
Malignancy – Primary or Metastatic cancer
Infection – Osteomyelitis or epidural abscess
Ankylosing spondylitis,
psoriatic spondylitis,
Reiter’s syndrome,
Inflammatory bowel disease
Rheumatoid arthritis
Osteochondrosis
Paget’s disease of bone
Ischial bursitis
Piriformis syndrome
Fibromyalgia
Polymyalgia rheumatica
Pancreatitis
Cholecystitis,
Duodenal Ulcer / penetrating ulcer
Prostatitis,
Endometriosis,
Pelvic inflammatory disease
Kidney stones
Pyelonephritis
Perinephric abscess
Prostatitis
Aortic aneurysm
Thinking: Causes of low back pain can be grouped into mechanical causes, non-mechanical causes, referred pain from the GI, pelvic area, aorta, kidneys etc.
Reference
http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/neurology/low-back-pain/