Arthritis
Over time, as discs wear out, bone spurs form and facets inflame, which can cause pain. A combination of these problems may cause or worsen stenosis, and can irritate nearby nerves, resulting in more pain.
Bulging Disc
Repeated flexion may cause your disc to dry out and degenerate at a young age. As your discs wear out, the inner, jellylike nucleus starts to bulge into the annulus (the tough outer, ring-like wall of the disc), causing both pressure and pain.
Fractures
Fractures are caused from either severe trauma or weakened bone. Some fractures can be treated with simple supports, while others require surgery.
Instability
As a disc stretches and flattens, the vertebrae slide back and forth and can create spine instability. If your disc stretches, the resulting pressure of the annulus may result in pain.
Muscle Spasms/Strain
This is the most common cause of low back pain, and may occur when one does repetitive movements. Additionally, lifting, a fall, or the performance of unusually strenuous exercise can result in painful pulling of the muscles, and those who are overweight are often at risk for lower back pain. Initially rest, ice, and medication may be helpful, but long term, physical activity is the key to complete recovery.
Ruptured Disc
The bulging of a disc causes the nucleus to move closer to the outer edge of the annulus. Furthermore, a sudden movement can cause your annulus to rupture, which often makes the nucleus push out and irritate the nerve.
Torn Annulus
A sudden movement may cause a tiny tear in your annulus which is often a result of a taut disc. Such tightness may cause the stretching of nearby ligaments to help compensate, and an individual may feel pain - as both the annulus and ligaments contain pain fibers.