Overview
Lumbago is the term used to describe general lower back pain. The exact cause of the lumbago/back pain is often unknown. The back pain can come on suddenly after lifting things, or gradually through overuse (see weak back) such as repetitive movements when decorating, gardening etc, or even for no obvious reason.
Causes
Lumbar disc herniation
Muscle strains
Facet joint pain
Spondylolysis
Postural problems such as lordosis and scoliosis
Ankylosing spondylitis
Sarcoiliac joint pain
Muscular trigger oints or myofascial pain in the buttocks or the paravertebral muscles
A general weakness in the back and core muscles
Muscle imbalances
Spinal canal stenosis
Poor workstation set-up or poor driving position
Diagnosis
Physical examination and medical history consultation
X-rays
MRI
CT scan
Treatment
Rest
Application of heat/ice
Ultrasound, TENS, or interferential treatment
Sports massage
Physical therapy
Anti-inflammatory/pain relieving/muscle relaxing medication
Source: http://www.sportsinjuryclinic.net/sport-injuries/low-back-pain/lumbago