TMTJ osteophytes have minimal effect on the career of STB racehorses. The impact after age 4 is still unknown.

Impact of periarticular osteophytes of the distal tarsus diagnosed in non lame yearling Standardbred horses on racing performance

Annette M McCoy , Kara N Scolman

Background
The study aimed to evaluate the radiographic prevalence of periarticular osteophytes in the distal tarsus of nonlame yearling Standardbred horses and assess their impact on racing performance. Periarticular osteophytes are recognized as markers of degenerative joint disease (DJD) but are not strongly correlated with clinical lameness in the distal tarsus. The study hypothesized that these osteophytes would negatively affect performance, with larger lesions having a greater impact.

Methods

A cross-sectional cohort study was conducted on 416 nonlame Standardbred yearlings from a single farm in the USA. Bilateral tarsal radiographs were reviewed for the presence and size of periarticular osteophytes, which were categorized into size-based groups. Racing records, including starts, wins, and earnings, were retrieved from the United States Trotting Association. Statistical analyses, including regression models, were employed to evaluate the associations between osteophyte presence or size and performance outcomes, adjusting for sex and gait.

Results
- Prevalence: Periarticular osteophytes were observed in 113 (27.1%) horses, predominantly affecting the tarsometatarsal joint, with bilateral involvement in 55.8% of cases.
- Performance Impact:
- Horses with osteophytes had fewer starts at 4 years (IRR 0.92, p = .01) and fewer lifetime starts (IRR 0.95, p = .003), but the effect size was minor.
- Among affected horses, larger osteophytes were associated only with fewer starts at 3 years (IRR 0.67, p < .0001).
- Gait (pacers vs. trotters) and sex significantly influenced performance, independent of osteophyte presence.
 
The overall racing performance of horses with osteophytes did not differ substantially from unaffected horses.
Limitations

The study was limited by a relatively small sample size of affected horses, potentially reducing statistical power. Follow-up data were limited to publicly available records, and other factors influencing performance could not be fully accounted for. Additionally, the analysis did not include other radiographic features of DJD that might influence outcomes.

Conclusions

Periarticular osteophytes in nonlame yearling Standardbred horses were common but had minimal impact on racing performance through at least 4 years of age. These findings suggest that the presence of such lesions should not be a primary concern for predicting racing potential. Further studies could explore the progression of osteophytes and their relationship to clinical signs of DJD over time.

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