Osteoarthritis is also known as degenerative joint disease.
It is a condition in which the protective cartilage that cushions the tops of bones degenerates, or wears down.
The low back contains five sets of facet joints, one on the left and one on the right side of each spinal bone.
These joints are quite small compared to the amount of body weight they bear.
The resulting stress and strain makes them susceptible to damage to the cartilage, and injury.
The accumulation of injuries over a lifetime causes the joints to break down, or degenerate.
The degenerative process is similar to what happens in a car.
If the shocks go out and aren’t replaced, the next thing that happens is that the springs break.
In the lower back, once the torn disc stops absorbing the stresses and strain of everyday life, the facet joints go out next.
When the facet joints are injured they become inflamed, swell, cause muscle spasm, and the back pain cycle begins.
Spinal arthritis causes stiffness and low back pain.
The stiffness is worst upon waking up in the morning, tends to ease with activity, then worsens toward the end of the day. Presumably, this is because fluid has built up in the joint due to inactivity overnight, which causes more swelling.

Dedicated to Alex Bürkli for his support. 🖤