Movement patterns in horses with multiple limb lameness

Sammanfattning: Disorders from the locomotion apparatus is the most common disease category in horses and a common cause for euthanasia. A frequent symptom of these disorders is lameness and to be able to treat such disorders the correct diagnosis needs to be made. Detecting lameness presents its difficulties due to limitations in the human visual ability, bias and the complexities of orthopaedic diseases and biomechanics. Lameness can emerge in one or multiple limbs and the mechanisms to decrease the loading of the affected limb often results in the misperception of lameness in other limbs, via a so-called compensatory lameness. Sometimes after a successful diagnostic analgesia of the primary lameness another lameness appears, revealing existing problems in multiple limbs. While the movement pattern of horses with unilateral and compensatory lameness is investigated in several studies, the movement pattern of horses with multiple limb lameness is not. The aim of this study was to investigate horses with multiple limb lameness and whether specific movement patterns can be indicative of multi limb lameness. This thesis included 193 horses that were recorded with the camera-based optical motion capture system (Q-horse by Qualisys) during routine lameness examinations by the veterinarians at four equine hospitals in Europe. Horses were included if they had an initial head or pelvic asymmetry above thresholds (HDmax and HDmin >|15|mm or PDmax and PDmin >|7|mm) that was reduced by at least 70% by diagnostic analgesia. Furthermore, they were divided into different groups depending on if they were considered lame on one or several limbs, or if they had a deviating movement pattern making them suspected to be multi limb lame. The result of the thesis shows no clear indicators of multiple limb lameness but gives indications that a horse with an ipsilateral forelimb and hindlimb lameness either can appear as a forelimb lame horse with a head and wither asymmetry indicating different forelimbs or as a hindlimb lame horse with a head and wither asymmetry indicating the same forelimb. The result also shows that a bilateral forelimb horse in some cases also have a head and wither asymmetry indicating different forelimbs as well as a bilateral hindlimb lame horse in some cases have a head and wither asymmetry indicating the same forelimb. It is though uncertain whether it is the bilateral lameness causing the deviating head and wither asymmetry pattern or another (third) lameness. This thesis is limited by the small study population and the difficulties to ensure that the horses only have the expected lameness, especially since the movement pattern of multiple limb lame horses is largely unknown. The possibility that the horses are lame in other limbs as well is a cause to possible errors in the study, since it can result in a misinterpretation of the movement pattern and erroneously comparing between the movement pattern of horses with lameness on one and multiple limbs.