Lumbar functional instability: a critical appraisal of the literature.

The goals of this paper were to define the concept of instability, to describe the way it can be assessed, to report on impairments of the spine stabilization system in patients with low back pain (LBP), to cite the recommended exercises and, lastly, to examine the results of programs based on lumbar stabilization. Patients suffering from lumbar instability appear to belong to a particular subgroup of subjects with LBP. In the literature, several definitions of lumbar instability have been proposed. Radiological instability, for instance, differs from functional instability. Diagnosis remains difficult: the relevance of static and dynamic radiographs appears limited whereas several signs and clinical instability tests have been described in the literature but remain controversial. The functional stability system of the spine consists of three interdependent components: the passive, the active and the neuromuscular subsystems. The benefits of lumbar stabilization programs for LBP patients have been underlined. Lumbar stabilization exercises are aimed at sensorimotor reprogrammation of spine stabilizer muscles intended to improve their motor control skill and delay of response and consequently to compensate for weakness of the passive stabilization system.