ABSTRACTBackground:Musculoskeletal injury is a major welfare and economic challenge in racehorses, with stress-related bone injury contributing to training interruption and catastrophic failure. Advanced imaging modalities can detect early skeletal pathology but remain limited in routine screening environments. Circulating biomarkers of bone turnover may provide complementary indicators of skeletal remodelling but require validation against objective imaging findings.Objectives:Evaluate whether osteocalcin (OC) and C-terminal telopeptide of type I collagen (CTX), or the CTX/OC ratio, are associated with scintigraphic abnormalities and lameness status in racehorses, and explore relationships with short-term adverse musculoskeletal outcomes.Study design:Prospective, observational case–control study.Methods:Ninety-six racehorses were enrolled, including 48 lame horses referred for scintigraphy and 48 clinically sound controls. Serum OC and CTX concentrations were measured by ELISA at the time of scintigraphic examination. Scans were classified as no abnormality detected (NAD), moderately positive (mPOS), or strongly positive (sPOS). Associations were assessed using non-parametric tests, logistic regression, and ROC analysis Clinically sound horses were followed for 28 days to record adverse musculoskeletal outcomes.Results:OC concentrations were higher in lame horses than in controls (mean difference 0.878 ng/mL, 95% CI 0.395–1.360) and differed across scintigraphic categories, with lower values in NAD horses than mPOS horses (mean difference 1.561 ng/mL, 95% CI 0.35–2.87). The CTX/OC ratio differed between NAD and positive scans in lame horses but not controls. Higher OC concentrations were associated with injury status (OR 9.75, 95% CI 2.82–49.38; AUC 0.75). In clinically sound horses (n=44), CTX showed modest discrimination for short-term adverse outcomes (AUC 0.68).Main limitations:Short follow-up duration, limited outcome events, and potential workload-related confounding at sampling.Conclusions:Serum osteocalcin concentrations were associated with lameness status and scintigraphic severity.Bone turnover markers may provide complementary biological information alongside imaging but  require validation in larger longitudinal studies.