BACKGROUND: Posterio-anterior (PA) movements are one type of passive intervertebral movement used to assess and treat perceived deficits in localized segmental mobility.

OBJECTIVES: To describe: 1) The specific effects that reductions in segmental mobility would be expected to have on PA movements; 2) How differences in PA movements in clinical situations compare to what would be expected with reduced segmental mobility; and 3) Whether such differences in PA movements are likely to be perceivable by manual palpation.

METHODS: Multiple modelling studies and in vivo measurements of PA movements are described.

RESULTS: The findings indicate the differences in PA movements present in clinical conditions corresponds with the differences that would be expected with decreased segmental mobility. The differences both predicted from the modelling and found in clinical conditions were greatest at low levels of force. Additionally, the differences are large enough that individuals with training are likely to be capable of 1) consistently producing controlled movements with sufficiently small magnitudes of force to assess the movements, and 2) detecting the differences in stiffness expected from modelling and found in clinical situations.

CONCLUSIONS: Implications for clinical practice and teaching include the need to attend to the stiffness of PA movements at lower levels of force than those typically described. The authors recommend a three tiered approach to assessment of PA movements which may assist in both clinical practice and teaching manual therapy skills.