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Keywords:

  • horse;
  • osteoarthritis;
  • small tarsal joint;
  • intra-articular anaesthesia;
  • radiography

Summary

Reasons for performing study: Despite the possibility that sound horses may have radiographic signs consistent with osteoarthritis of the small tarsal joints (OA-STJ), a diagnosis of ‘bone spavin’ as a cause of lameness is often made based only on radiographic examination.

Objectives: To determine whether severity of radiographic change and response to treatment are correlated with the duration and degree of lameness and the response to intra-articular anaesthesia in horses with OA-STJ.

Methods: A retrospective study of all horses that showed a positive response to intra-articular anaesthesia of the STJ was performed. Details of history, clinical presentation and diagnostic findings were recorded. Radiographs of affected tarsi were evaluated and scored independently by 2 observers. Follow-up was via a telephone questionnaire with the owner. Statistical analysis was used to assess the association between the duration and degree of lameness, the response to intra-articular anaesthesia and radiographic findings. Response to treatment was compared with the findings from the diagnostic work-up.

Results: Ninety-one horses were included (61 unilateral and 30 bilateral lameness). Fifty-nine percent of horses had been lame for over 2 months. There was no association between the duration and degree of lameness, or between duration or degree of lameness, intra-articular anaesthesia and radiographic findings. Response to treatment showed a significant positive association with less severe radiographic changes within the tarsometatarsal (TMT) joint. Follow-up was available for 48% of cases, with 52% horses returning to the same level of exercise.

Conclusions: There is no association between the duration and degree of lameness, the response to intra-articular anaesthesia and radiographic findings in horses with OA-STJ. However, horses that improved following treatment tended to have less marked TMT joint pathology.

Potential relevance: Response to intra-articular anaesthesia should remain the gold standard for diagnosis of OA-STJ. Predicting which cases are likely to improve following treatment remains difficult.