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Equine veterinary journal2025; doi: 10.1111/evj.70106

Computed tomography features of the fetlock joint in elite racing Thoroughbred horses.

Abstract: Computed tomography (CT) is increasingly used for metacarpo/tarsophalangeal or fetlock joint (MC/TPJ) evaluation in Thoroughbred racehorses. CT features and lesion prevalence in competing Thoroughbreds are unknown. Objective: To identify standing CT features within the MC/TPJ of elite Thoroughbred staying racehorses. Methods: Retrospective cohort study. Methods: Computed tomography scans of the MC/TPJ were performed as part of pre-race screening for fracture risk and graded for CT features. Descriptive statistics and univariable logistic regression models were generated to investigate associations with presence of palmar osteochondral disease (POD), parasagittal groove subchondral lysis and fissure. Results: A total of 406 limbs from 86 horses were scanned; 72 horses were scanned once, 12 horses were scanned twice, and two horses scanned three times. POD was common, being present in 74/86 (86.0%, 95% CI 76.9-92.6) horses and in 231/342 (67.5%, 95% CI 62.3-72.5) limbs on first scan. POD was associated with more career race starts (p = 0.05) but fewer placings per start (p = 0.008). Parasagittal groove (PSG) lysis, previously associated with condylar fracture, was observed in 16/86 (18.6%; 95% CI 11.0-28.4) horses and 20/342 (5.8%; 95% CI 3.6-8.9) limbs on the first scan, whereas fissures in this region, which are not associated with fracture, were observed in 41/86 (47.7%; 95% CI 36.8-58.7) horses and 65/342 (19.0%; 95% CI 15.0-23.6) limbs. Osteoarthritis of the fetlock joint was uncommon. Conclusions: Horses travelling from overseas had undergone prior screening of their fetlock joints, predominantly with MRI, likely reducing the prevalence of pathology in these horses. Conclusions: POD is common in elite staying Thoroughbred racehorses, however, negatively impacts performance. The prevalence of PSG lysis supports the use of CT screening of high-risk populations of Thoroughbred racehorses in fracture risk management. Further work is required to determine if these findings are applicable more generally to other racing Thoroughbreds.
© 2025 EVJ Ltd.
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Publication Date: 2025-10-18 PubMed ID: 41108534DOI: 10.1111/evj.70106Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study analyzed computed tomography (CT) scans of the fetlock joint in elite Thoroughbred racehorses to identify common bone and joint features and lesions.
  • The goal was to understand the prevalence of certain bone diseases and how they relate to racing performance and fracture risk.

Background and Purpose

  • The fetlock joint, also called the metacarpo/tarsophalangeal joint (MC/TPJ), is a critical joint in a horse’s leg involved in racing movement.
  • Computed tomography (CT) is increasingly used to evaluate this joint for bone lesions and damage that could indicate fracture risk.
  • Prior to this study, CT features and the prevalence of lesions in competing elite Thoroughbreds were not well characterized.
  • The objective was to identify and describe the standing CT findings of the fetlock joint in elite staying Thoroughbred racehorses and assess associations between lesions and factors such as performance.

Methods

  • This was a retrospective cohort study, analyzing past CT scans taken as part of pre-race screening.
  • A total of 406 limbs from 86 elite Thoroughbred horses were scanned using CT.
  • Most horses had one scan, while some had two or three scans over time.
  • Specific lesions and features were identified and graded, particularly focusing on:
    • Palmar osteochondral disease (POD)
    • Parasagittal groove (PSG) subchondral bone lysis
    • Fissures in the PSG region
  • Statistical analyses included descriptive statistics and univariable logistic regression to examine links between lesions and racing metrics.

Key Findings

  • Palmar osteochondral disease (POD):
    • Highly prevalent, found in 86% of horses and 67.5% of limbs on first scan.
    • POD was associated with a greater number of career race starts, suggesting it develops with racing exposure.
    • However, horses with POD had fewer placings per start, indicating a potential negative impact on racing performance.
  • Parasagittal groove (PSG) lesions:
    • PSG lysis, which is associated with a higher risk of condylar fractures, was present in 18.6% of horses and 5.8% of limbs.
    • PSG fissures, which are not linked to fractures, were observed in almost half of the horses (47.7%) and 19% of limbs.
  • Osteoarthritis:
    • Osteoarthritis of the fetlock joint was found to be uncommon in this cohort.

Interpretation and Implications

  • Many overseas horses had prior fetlock joint screening, often with MRI, which may explain the relatively lower prevalence of pathological lesions in some cases.
  • The high prevalence of POD highlights it as a common racing-related condition that may hinder performance.
  • The presence of PSG lysis, a known fracture risk factor, supports the use of CT screening for early detection and management of fracture risk in high-level Thoroughbred racehorses.
  • Since findings are from elite staying racehorses, further studies are needed to see if these results apply to other Thoroughbred populations worldwide.

Conclusions

  • CT imaging reveals that palmar osteochondral disease is widespread in elite Thoroughbred racehorses but has negative effects on racing success.
  • CT can also identify parasagittal groove lytic lesions that are associated with fracture risk, supporting its role in pre-race screening protocols.
  • This research provides a valuable baseline understanding of fetlock joint CT features in elite racers, with potential to improve injury prevention strategies.

Cite This Article

APA
Beck C, Hitchens PL, Muir P, Whitton RC. (2025). Computed tomography features of the fetlock joint in elite racing Thoroughbred horses. Equine Vet J. https://doi.org/10.1111/evj.70106

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Beck, Catherine
  • Melbourne Veterinary School, Faculty of Science, University of Melbourne, Melbourne, Victoria, Australia.
Hitchens, Peta L
  • Melbourne Veterinary School, Faculty of Science, University of Melbourne, Melbourne, Victoria, Australia.
Muir, Peter
  • Department of Surgical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Whitton, R Christopher
  • Melbourne Veterinary School, Faculty of Science, University of Melbourne, Melbourne, Victoria, Australia.

Grant Funding

  • Racing Victoria Ltd
  • Victorian State Government
  • University of Melbourne
  • Victorian Racing Industry Fund

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