The arthritis describes age related changes that affect joints. Although everyone will experience age related joint changes the degree of these changes will vary for each individual and not everyone will experience symptoms. The specific changes that occur can be summarised as follows:

The cartilage (smooth joint surfaces) wears and becomes thinner.

The joint capsule (fibrous tissue that surrounds the facet joint) becomes thickened and stiff.

The muscles that support the facet joints may weaken also.

The lumbar intervertebral discs have a tough, fibrous, outer layer that surrounds a soft gel core. Due to this structure the discs provide shock absorption and are flexible allowing normal lumbar spine movements. An Intervertebral disc pain describes a condition where the discs soft gel core pains through a weakness or tear in the fibrous outer layer.

The lower back nerve roots lie in a small space to each side of the lumbar joints. With injury or as a normal age related process the intervertebral discs and/or facet joint scan extend into and narrow this space. This can irritate the nerve root(s).