The effects of sacroiliac manipulation on arthrogenic muscle inhibition in the hip musculature in patients with sacroiliac syndrome
In symptomatic sacroiliac syndrome, nociceptors located within the capsule and ligaments of the sacroiliac joint are said to be activated which in turn act on inhibitory interneurons that synapse with the motor neuron pool of the muscles of that joint (muscles responsible for hip flexion, extension, abduction and adduction fall within the sacroiliac motor neuron pool). These inhibitory interneurons relay information that decreases the recruitment ability of that motor neuron pool. This is termed Arthrogenic muscle inhibition (AMI) and it has been stated that the number of motor units innervating a muscle relates positively to the strength of that muscle and hence may have an effect on the functional ability of that muscle. However, it has been proposed that spinal manipulation activates mechanoreceptors (Wyke receptors) from structures in and around the manipulated joint causing changes in motor neuron excitability through the altered afferent input and thereby causing an increase in motor neuron recruitment and a decrease in AMI. Furthermore, it has been found that sacroiliac joint problems have often been related to reduced or asymmetric range of motion (ROM) of the hip and / or lack of proprioceptive ability in the ipsilateral limb. In light of the above, manipulation has been found to cause a re-establishment of normal muscle tone and joint kinematics, therefore relaxing the muscles in that area and restoring normal ROM of the involved joint. This study presents the results of sacroiliac manipulation on objective hip measures (including peak torques, ROM and proprioception).