Spinal Instability – Description

When the discs in the spine start to degenerate they lose disc height and disc tension (turgor), leading to slackening of the surrounding ligaments. The core muscles of the spine and deep abdomen often become “switched off” as part of the body’s reaction to chronic back pain. These factors then result in the development of abnormal micromovements of one vertebra on another. This micro-shearing movement can cause further wear and tear on the disc and facet joints as well as nipping (impinging) the nerve root next to the disc in the foramen.

The loss of disc height and tension can result in dynamic anterior (olisthesis / spondylolisthesis) or backward (retrolisthesis) slippage during flexion and extension movements. In turn this strains the capsule of the posteriorly placed facet joints and increases the travel of the facet joint surfaces beyond their normal limits and matching (congruent) alignment.  In time this causes the arthritic wear in the joint and compensatory enlargement of the joint surfaces, with further encroachment into the foramen and spinal canal in addition to impingement upon the exiting and descending nerves.

The “sloppiness” of the degenerate disc level potentially allows the:

  • disc to distort the nerve if it is tethered to the disc
  • superior foraminal ligament to impact into the nerve in the superior foramen
  • facet joint and associated osteophytes to impact into the nerve in the mid foramen
  • vertebral shoulder osteophyte to impact into the anterior surface of the nerve
  • (reactive) scarring to entrap the nerve and aggravate the nerve irritation
The repeated displacement of the two surfaces of the facet joint causes stretching of the joint capsule and may also cause an area of thinning and weakness through which the lining of the joint may extrude. This out-pouching may form fluid in its own right, thus forming a sac of fluid which becomes surrounded by an isolating wall called a “Facet Joint Cyst“. In some patients the cysts may fill by fluid expressed from within the facet joint through a narrow neck which acts as a one way valve. Facet joint cysts may be asymptomatic if they become large enough to compress the exiting of descending nerve roots at that level.

The symptoms of “instability” are those of back, buttock and leg pain aggravated by postural change, rotation, vibration or impact. Typically the back will suffer a stabbing “catch” as you stand upright or get out of a chair. The back may feel weak and pain may increase when attempting to stand upright.


Our approach to treatment is based on the conventional conservative management of core muscle strengthening and postural rehabilitation, together with paraspinal dry needling and manual stretching delivered by our osteopaths or physiotherapists to restore muscle balance and tone. Intervertebral Differential Dynamics (IDD Therapy) may help to restore some disc height and turgor.

In the case of facet joint symptomatic facet cysts we often advise these to be tackled as the first priority either by x-ray or CT guided aspiration and / or injection or endoscopic spinal surgery.

Therapeutic facet injections (facet joint injections, root blocks etc) may act as an adjunct in order achieve a pain free window during which core strengthening exercises may be more effective.

In chronic cases where this conservative regimen fails, patients may need to consider spinal surgery, for example Anterior or Posterior Lumbar Interbody Fusion or Total Disc Replacement, Transforaminal Endoscopic Minimally Invasive Spine Surgery.