Musculoskeletal Pain: What the Research Says
Evidence from 19 peer-reviewed studies
What Professionals Should Know
- •Acetaminophen at 30 mg/kg may offer faster pain relief in acutely lame horses compared to traditional NSAIDs like phenylbutazone, with effects visible within 2-4 hours
- •This small study suggests acetaminophen could be a useful alternative or adjunct therapy for acute lameness, but safety and efficacy of repeated dosing requires further investigation before routine clinical adoption
- •Heart rate response differed between treatments, suggesting acetaminophen 30 mg/kg may have additional physiological effects beyond analgesia that warrant further study
- •Riders and owners often present horses to competition with subtle pain behaviours unrecognized as lameness; learning the 24 behaviours in the RHpE can help identify these horses and prevent welfare compromise
- •Low-level event horses show higher pain behaviour scores than elite dressage horses, suggesting different training methods or populations; consider ethogram assessment when investigating performance issues at lower levels
- •Recognition and elimination of pain behaviours before they manifest as overt lameness may improve both horse welfare and ridden performance, including rider confidence and safety
- •Acetaminophen at 30 mg/kg twice daily is safe for 21 days with no hepatic or gastric toxicity concerns in chronic lameness cases
- •Short-term subjective improvement occurs within 2-4 hours post-dose, but this transient effect suggests acetaminophen alone is insufficient for managing chronic lameness
- •Consider acetaminophen as an adjunctive rather than standalone therapy, combining with other pain management strategies for better clinical outcomes
- •Horses with poor performance may have underlying musculoskeletal pain even without overt lameness signs; use RHpE to identify subtle pain indicators during ridden work
- •Saddle fit should be routinely evaluated as a significant contributor to performance issues—37% of poor performers in this study had ill-fitting saddles
- •Diagnostic anaesthesia combined with saddle adjustment can substantially improve ridden gait quality and reduce pain-related behavioural signs, making it a valuable diagnostic and therapeutic approach
- •Use the 24-behavior RHpE during warm-up to identify horses at risk of cross-country failure; a score ≥7 suggests 59% failure rate and warrants further veterinary investigation before competition
- •Higher RHpE scores correlate with worse dressage performance and final placings, so systematic assessment can inform both welfare decisions and competitive expectations
- •The RHpE is a repeatable, practical tool for detecting subtle musculoskeletal pain early, enabling earlier diagnosis and treatment to improve both welfare and performance outcomes
- •Always assess ridden horses for lameness and gait abnormalities, as nearly 2/3 showed problems only when ridden—in-hand assessment alone will miss significant issues affecting performance and welfare
- •Check saddle tree point fit carefully and ensure riders sit in the middle of the saddle rather than towards the back; these factors directly correlate with horse pain and discomfort
- •Reconsider use of crank cavesson nosebands in favour of standard cavessons or no noseband, as they are associated with higher pain indicators independent of actual mouth opening restriction
- •Improved rider skill reliably produces measurable improvements in gait quality, supporting investment in rider training and education
- •RHpE scores alone may not capture how rider skill influences horse movement; assessment should include objective gait evaluation alongside pain ethogram scoring
- •Rider technique can modulate how pain behaviours are expressed—a horse's pain indicators may vary depending on who is riding, so serial assessments should use consistent riders when diagnosing musculoskeletal issues
- •The Ridden Horse Pain Ethogram is a practical tool for identifying musculoskeletal pain in working horses; an RHpE score of 8 or higher warrants veterinary evaluation even when lameness appears subtle
- •Owner/rider perception of horse comfort is unreliable—over 70% of horses in this 'comfortable' sample showed detectable lameness, emphasizing the need for objective assessment methods
- •Rider skill significantly influences pain expression; investment in rider training may improve both horse welfare outcomes and the reliability of pain assessments during ridden work
- •The Ridden-Horse-Ethogram is a reliable, trainable assessment tool that veterinarians can use in real time during ridden evaluations to identify lame or painful horses without requiring video analysis or extended observation periods.
- •This behavioral scoring system helps differentiate true lameness from other performance issues (poor saddle fit, rider skill, or muscle tension alone), allowing you to direct diagnostic efforts more efficiently.
- •After appropriate training, any veterinarian can achieve consistent application of this ethogram, making it a practical addition to lameness examinations and potentially reducing reliance on extensive subjective observation or repeat visits.
- •Misbehaviour should be evaluated as a potential indicator of underlying musculoskeletal pain rather than assumed to be purely behavioural, prompting veterinary assessment
- •Understanding risk factors for misbehaviour in young/amateur horses can help inform preventive management strategies to reduce both performance issues and rider safety incidents
- •Pony Club horse handlers should be educated on misbehaviour as a multi-factorial issue involving pain, performance, and safety considerations
- •Pressure algometry offers an objective, repeatable method to quantify musculoskeletal pain in horses, providing an alternative to subjective palpation alone for assessing sacroiliac dysfunction
- •Lower pressure thresholds and side-to-side asymmetry detected by algometry can help confirm clinical suspicion of SID and monitor response to physiotherapy or treatment interventions
- •This technique enables practitioners to document pain objectively, track changes over time, and make evidence-based decisions about treatment efficacy in horses with suspected SID
- •Pressure algometry is a promising objective tool for locating and documenting back pain in horses, potentially improving diagnostic accuracy beyond palpation alone.
- •The method shows good repeatability, making it suitable for tracking pain changes over time and monitoring response to treatment.
- •Further clinical validation is needed before pressure algometry can be routinely recommended for musculoskeletal injury assessment in practice.
- •The adapted RHpE is a repeatable tool for identifying pain in ridden Icelandic horses and may help detect lameness that riders assume is absent — consider using it alongside traditional lameness assessment
- •The very high prevalence of pain indicators (96%) in this population suggests systematic assessment of ridden horses for pain is warranted in routine practice
- •Caution needed when interpreting RHpE scores in Icelandic horses until validation is completed with non-lame horses in properly fitted tack; current threshold may need adjustment for this breed
- •FES offers a diagnostic tool to isolate specific musculoskeletal and neuromuscular dysfunction in static position, potentially improving diagnostic accuracy compared to ridden or lunged assessment
- •The controlled movement data from FES can help develop targeted rehabilitation protocols by identifying precise regions of dysfunction
- •FES may reduce diagnostic ambiguity arising from compensatory movement patterns and environmental variables in routine clinical evaluation
- •A standardized 24-behaviour ethogram can objectively identify low-grade lameness that may be missed by conventional assessment; look for ≥8 markers as an indicator of pain
- •This tool is useful for longitudinal monitoring to assess whether treatment interventions (farrier work, injections, physiotherapy) are actually improving the horse's movement quality
- •Untrained observers can apply the ethogram with consistency, though training improves reliability—consider using video-based assessment as part of lameness diagnosis and management decisions
- •Bell boot therapy combined with structured proprioceptive training may help correct muscle imbalances in horses, but requires careful monitoring to prevent compensatory asymmetries developing in opposite directions
- •Asymmetries detected during circle work may be directional and require targeted training in both directions to avoid overcompensation
- •This represents a non-invasive rehabilitation approach for managing functional muscle imbalances, though results are based on a small sample size
- •Use the 24-behaviour RHpE checklist during 10-minute ridden assessments (walk, trot, circles, canter, transitions) to detect pain that may not appear as obvious lameness
- •A score of ≥8/24 behaviours warrants veterinary investigation for musculoskeletal issues—this tool helps identify subtle pain that affects performance and welfare
- •Check saddle fit, rider weight, and rider position on the saddle as potential contributors to pain behaviours; the RHpE provides an objective way to discuss these issues with clients without blame
- •Consider acupuncture and spinal manipulation as complementary pain management tools for geriatric horses with chronic laminitis or osteoarthritis when conventional treatments are insufficient
- •Integrative therapies may help manage musculoskeletal stiffness and muscle hypertonicity in aged horses, potentially improving comfort and function
- •These approaches provide additional diagnostic and management options for the growing population of senior horses in practice
- •Use composite pain scales or facial expression assessments as the most validated objective methods for evaluating your horse's pain response to treatment
- •Standardized pain assessment tools can help you and your veterinarian communicate more clearly about pain severity and track treatment effectiveness over time
- •Objective pain scales are increasingly important for evaluating new pain management strategies and ensuring better welfare outcomes in hospitalized and ridden horses
Key Research Findings
Acetaminophen 30 mg/kg achieved peak plasma concentration of 30.02 μg/ml within 0.43 hours, compared to 20.01 μg/ml at 0.66 hours for the 20 mg/kg dose
Acetaminophen 30 mg/kg produced significantly lower heart rate compared to acetaminophen 20 mg/kg, phenylbutazone, and placebo at multiple time points (1-8 hours post-treatment)
Lameness scores improved significantly with acetaminophen 30 mg/kg versus placebo at 2 and 4 hours post-treatment; phenylbutazone showed significant improvement only at 8 hours
No significant differences in lameness improvement were detected between acetaminophen 20 mg/kg, acetaminophen 30 mg/kg, and phenylbutazone when directly compared
Median RHpE score across all 1358 competition horses was 4 (IQR 2-5), with median lameness grade 0 (IQR 0-1), indicating pain behaviours present even in subjectively non-lame horses
Significant difference in RHpE scores between low-level ODE (highest median scores) and GP dressage (p = 0.001), but no difference between 5* TDE and low-level ODE (p = 0.09)
Chi-square/Fisher's exact test identified significant differences in prevalence of 24 RHpE behaviours between non-lame and lame horses, indicating the ethogram can discriminate pain states
Acetaminophen 30 mg/kg PO every 12 h achieved Cmax of 20.83 ± 10.25 μg/mL on day 7 with Tmax of 0.40 ± 0.22 h
Subjective lameness scores significantly improved at 2 and 4 h post-treatment, with significant PDmax improvement in hindlimb lameness at 1, 2, and 8 h post-treatment
No clinically significant changes detected in clinicopathological analysis, hepatic biopsy, or gastric ulceration scores following 21 days of treatment
Acetaminophen produced only transient improvement and may not be effective as monotherapy for chronic lameness
Median RHpE scores decreased significantly from 9/24 before intervention to 2/24 after diagnostic anaesthesia and saddle change (p < 0.001)
34.7% of horses showed bilaterally symmetrical short step length and/or restricted hindlimb impulsion despite only 30% being continuously lame
No correlation existed between RHpE score and maximum lameness grade before diagnostic anaesthesia (Spearman's rho = 0.09, p = 0.262)
37.3% of horses had ill-fitting saddles considered likely to influence performance
Evidence Base
Pharmacokinetics and clinical efficacy of acetaminophen (paracetamol) in adult horses with mechanically induced lameness.
Mercer Melissa A, McKenzie Harold C, Byron Christopher R et al. (2023) — Equine veterinary journal
Determination of Equine Behaviour in Subjectively Non-Lame Ridden Sports Horses and Comparison with Lame Sports Horses Evaluated at Competitions.
Dyson Sue, Pollard Danica (2024) — Animals : an open access journal from MDPI
Pharmacokinetics, clinical efficacy and safety of acetaminophen (paracetamol) in adult horses with naturally occurring chronic lameness.
Mercer Melissa A, Davis Jennifer L, McKenzie Harold C et al. (2024) — Equine veterinary journal
Application of the Ridden Horse Pain Ethogram to 150 Horses with Musculoskeletal Pain before and after Diagnostic Anaesthesia.
Dyson Sue, Pollard Danica (2023) — Animals : an open access journal from MDPI
Application of a Ridden Horse Pain Ethogram to horses competing at 5‐star three‐day‐events: Comparison with performance
Dyson S., Ellis A. D. (2022) — Equine Veterinary Education
Gait abnormalities and ridden horse behaviour in a convenience sample of the United Kingdom ridden sports horse and leisure horse population
Dyson S., Routh J., Bondi A. et al. (2022) — Equine Veterinary Education
The influence of rider skill on ridden horse behaviour, assessed using the Ridden Horse Pain Ethogram, and gait quality
Dyson S., Martin C., Bondi A. et al. (2022) — Equine Veterinary Education
Application of a Ridden Horse Pain Ethogram and Its Relationship with Gait in a Convenience Sample of 60 Riding Horses.
Dyson Sue, Pollard Danica (2020) — Animals : an open access journal from MDPI
Can veterinarians reliably apply a whole horse ridden ethogram to differentiate nonlame and lame horses based on live horse assessment of behaviour?
Dyson S., Thomson K., Quiney L. et al. (2020) — Equine Veterinary Education
Misbehaviour in Pony Club horses: incidence and risk factors.
Buckley P, Morton J M, Buckley D J et al. (2013) — Equine veterinary journal
Pressure algometry to quantify muscle pain in racehorses with suspected sacroiliac dysfunction.
Varcoe-Cocks K, Sagar K N, Jeffcott L B et al. (2006) — Equine veterinary journal
Pressure algometry for the detection of induced back pain in horses: a preliminary study.
Haussler K K, Erb H N (2006) — Equine veterinary journal
Application of a Ridden Horse Pain Ethogram in Icelandic horses: A pilot study
Garcia Helene Dragelund, Lindegaard Casper, Dyson Sue (2023) — Equine Veterinary Education
Functional Electrical Stimulation (FES) in the Diagnosis and Treatment of Musculoskeletal and Neuromuscular Control Abnormalities in Horses - Selected Case Studies.
Schils Sheila, Ober Timothy (2022) — Journal of equine veterinary science
Application of a ridden horse ethogram to video recordings of 21 horses before and after diagnostic analgesia: Reduction in behaviour scores
Dyson S., Van Dijk J. (2020) — Equine Veterinary Education
The Efficacy of Intermittent Long-term Bell Boot Application for the Correction of Muscle Asymmetry in Equine Subjects.
Jensen Anne-Mette, Ahmed Waqas, Elbrønd Vibeke S et al. (2018) — Journal of equine veterinary science
The Ridden Horse Pain Ethogram
Dyson S. (2022) — Equine Veterinary Education
Pain management for laminitis in the horse
K. Hopster, A. V. Eps (2018) — Equine Veterinary Education
Objective pain assessment in horses (2014-2018).
van Loon J P A M, Van Dierendonck M C (2018) — Veterinary journal (London, England : 1997)