To date there are large gaps in the knowledge about the phenomenon of neck pain in the horse. This dissertation, which consists of four studies, aims to elucidate neck pain in the horse based on the concepts of neuromotor control and dynamic stability associated with neck pain in people. The first study describes the anatomy and morphology of two perivertebral muscles, namely, m. multifidus cervicis and m. longus colli. Both muscles are closely associated with neuromotor control and dynamic stability in people with neck pain. Based on findings in dissection, their anatomy and morphology are similar to those in people. As such, both muscles may play a role in vertebral stability in the neck of the horse. The second study investigated the prevalence and severity of osseous degenerative lesions in the articular process articulations of the equine cervical and cranial thoracic spine. Based on grading of osseous lesions of the articular process articulationsin this anatomical region, osseous degeneration is most prevalent in the mid-cervical and cervicothoracic region, and more prevalent in older and larger horses. In the first part of the third study, a technique was developed for repeatability of measurement of the cross-sectional area of m. multifidus cervicis and m. longus colli in the equine cervical spine, using ultrasound imaging. In the second part of this study, intra- and inter-operator repeatability was determined for measurement of the cross-sectional area of m. multifidus cervicis and m. longus colli in the equine cervical spine, using the ultrasound imaging technique that was developed in the first part of the study. Evaluation of the size of both muscles is of particular interest in programs of therapeutic rehabilitation, which aim to increase the size of perivertebral muscles to improve vertebral stability and reduce the recurrence of episodes of neck pain, particularly those associated with osseous degenerative changes in the cervical spine. Results from this study show that US is a repeatable technique for CSA measurement of m. multifidus cervicis and m. longus colli at specific levels of the equine cervical spine. The fourth study used behavioral responses from horses during a manual examination to develop an ethogram of specific behaviors that may be observed in manual examination of horses with neck pain. Distinct aversive behavioral responses from manual palpatory assessment and mobilization techniques in the cervical spine and cervicothoracic junction of horses were identified in some horses with neck pain. This study also investigated whether manual examination techniques could be applied in the equine cervical spine to identify horses with diagnosed neck pain as compared to control cases. In blinded examination, the manual therapy practitioner who carried out the evaluations was able to correctly place each horse into its respective category of neck pain versus control subject, according to responses from the manual examination techniques that were applied to the subjects. Together, this series of studies adds to current knowledge in the phenoment of equine neck pain, and widens the base for further investigation into dysfunction of the equine cervical spine.
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