378


EQUINE VETERINARY EDUCATION / AE / july 2022


We expect to observe substantial reduction in RHpE


scores after abolition of pain using diagnostic anaesthesia, assuming that the saddle fits adequately (Dyson et al. 2018b; Dyson and Van Dijk 2020). However, in some horses the behaviour ‘Front of head ≥30⁰ in front of vertical for ≥10 s’ may change to ‘Front of head ≥ 10⁰ behind vertical for ≥ 10 s’ (Dyson and Van Dijk 2020). Factors influencing head and neck position in ridden horses are discussed elsewhere (Dyson et al. 2020d). A bilateral hindlimb toe drag may persist or develop after diagnostic anaesthesia of the hindlimbs. A crooked tail may persist despite improvement in gait (Dyson and Van Dijk 2020; Hibbs et al. 2021). Crooked tail carriage was abolished in only 12% (20/164) horses in which hindlimb gait abnormalities were improved by diagnostic anaesthesia (Hibbs et al. 2021).


Other factors to consider when assessing ridden horses


There are a number of other factors which need to be considered when assessing ridden horses which were not assessed during the development of the RHpE because of variation in horse fitness, environmental conditions, the accuracy of audio recordings of horses and observations which cannot be quantified but can be communicated via the rider. These are subjective observations, but have been repeatable (Dyson et al. 2018b; Dyson and Van Dijk 2020), although the underlying cause may be multifactorial. The change in observations after resolution of underlying musculoskeletal pain using diagnostic anaesthesia lends credence to cause and effect. Sweating or a respiratory


rate which are disproportionate to the work intensity, horse fitness and environmental temperature are likely indicators of musculoskeletal pain. There may be an increase in respiratory noise in movements or gaits which the horse finds biomechanically more demanding. Repeated teeth grinding usually reflects discomfort. There are aspects of behaviour and movement which require the assessor to communicate with the rider, for example horse tension and rideability (the horse’s acceptance of, and responsiveness to, the rider’s cues), the range of motion of the thoracolumbosacral region and the impulses generated through the rider’s back, and the way in which the rider’s pelvis is moved during canter (Dyson 2016a, 2017). Rein tension may be altered, with either lack of rein tension (Fig 6b), excessive rein tension (the horse ‘hanging’ on the rider’s hands) or asymmetrical rein tension (the horse ‘leaning’ on one side of the bit, which is reflected by bit position in some horses [Fig 3a]). In association with hindlimb lameness the saddle may consistently slip to one side (Greve and Dyson 2013; 2014) (Fig 6a,b). Finally, snorting or nose blowing are often observed after improvement in lameness by diagnostic anaesthesia (Dyson et al. 2018b), presumably reflecting improved comfort and a positive emotional state (Stomp et al. 2018, 2020). It must also be recognised that oral, ocular or visceral


pain (for example equine gastric ulcer syndrome) can contribute to pain in ridden horses and result in alterations in behaviour (Kjærulff and Lindegaard 2022). However, it must also be borne in mind that gastric ulceration may develop secondary to chronic musculoskeletal pain and resolution of the ulcers may not improve ridden horse behaviour (Dyson et al. 2022b).


© 2021 EVJ Ltd


When to use the RHpE


There are multiple potential uses for the RHpE. Many equine clinicians have faced the situation when an owner fails to recognise or refuses to acknowledge that their horse has a combination of problems, resulting in chronic musculoskeletal pain, for which there is a guarded prognosis for pain-free ridden exercise. The RHpE provides an additional means of communicating with, and educating, the owner. The RHpE also provides a diplomatic means of illustrating to an owner that there may be an unacceptable imbalance between horse and rider size, and can be used to demonstrate the effect of the rider’s position in the saddle. The RHpE enables owners, veterinarians and other


paraprofessionals to recognise the presence of subclinical problems, which merit further investigation by a veterinarian skilled at the investigation of ridden horse problems. Early recognition of musculoskeletal pain and accurate diagnosis will facilitate effective long-term management and improve both performance and equine welfare. At a pre-purchase examination the aim is to be a


detective, to determine the risks involved with purchase of a horse for a specific purpose, for a specific rider. Any tool which gives additional information is of potential value. The RHpE has been routinely applied at pre-purchase examinations for several years (S. Dyson, unpublished data). There are circumstances when horses have been coping at their current work level, with their regular rider, and appear to move symmetrically, but do not move with normal fluidity, do not have normal range of motion of the thoracolumbosacral region and have restricted gaits. If the RHpE score is ≥ 8/24 this provides additional information that there is likely to be underlying musculoskeletal pain. Purchasers are advised accordingly of the potential risks. Horses purchased despite these discussions have been observed to subsequently deteriorate and require long-term management to maintain adequate comfort (S. Dyson, unpublished data). The RHpE can be used to assess a horse’s response to the


fit of a saddle for both the horse and the rider. An association between both tight saddle tree points and the rider sitting on the caudal one-third of the saddle and the RHpE score has been documented (Dyson et al. 2022a). Skilled saddle-fitters have long-recognised a relationship between saddle-fit and equine behaviour (Schleese 2014). When investigating poor performance in ridden horses the


use of diagnostic anaesthesia is crucial for identifying the source(s) of pain (Dyson 2016b). The response to diagnostic anaesthesia can be evaluated by the presence or absence of lameness, the quality of the horse’s gaits and the horse’s behaviour. If there is not substantial reduction in the RHpE score it implies that there is residual pain, requiring further investigation. When differentiating trigeminal-mediated head shaking behaviour with head tossing behaviour in ridden horses, secondary to musculoskeletal pain, the RHpE can be used to support the likely presence of musculoskeletal pain (Thomson et al. 2020). The RHpE score has provided evidence that idiopathic hopping-type forelimb lameness in ridden horses (Dyson and Rasotto 2016) is likely to be pain-induced (Dyson 2020). This is despite no response to systemically administered analgesic medication, and no change or deterioration in lameness following diagnostic anaesthesia, possibly because the lameness is associated with neuropathic pain (Dyson 2020).


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88