Variability of forces applied by experienced physiotherapists during provocation of the sacroiliac joint

Objective. To evaluate the distribution of total force vector and force components intended for the right and left sacroiliac joint, respectively, during pain-provocation sacroiliac joint tests. Design. Two force plates, each capable of sensing three orthogonal forces, were used in a descriptive study to assess force. Background. Studies evaluating the reliability of sacroiliac joint tests have revealed conflicting results and to our knowledge, no studies have evaluated the distribution of forces and their variations. Methods. Fifteen physiotherapists, experienced in musculoskeletal therapy, performed the distraction test and pressure on apex sacralis on the same healthy person on two occasions. Results. In both tests, the total force vector was less on the force plate closer to the physiotherapist. The vertical force component dominated and was considerably greater than the lateral (examined person supine/prone). The caudal/cranial force component was small. Systematic differences were found for the total force vector and for the lateral and vertical force components between occasions and/or between the force plates. Conclusions. The consistency of total force vector and force components was incomplete within and between physiotherapists and between occasions.