Effect of high-speed exercise on subchondral bone in the metacarpo-/metatarsophalangeal joints of 2-year-old Thoroughbred racehorses in their first year of training.
Authors: Ciamillo, Bills, Gassert, Richardson, Brown, Stefanovski, Ortved
Journal: Equine veterinary journal
Summary
# Editorial Summary Repetitive high-speed exercise during the critical first year of racehorse training accumulates measurable structural changes within the subchondral bone of the fetlock joint, according to this longitudinal study of 41 two-year-old Thoroughbreds monitored over 12 months using standing cone-beam CT imaging. Researchers tracked both adaptive bone responses (sclerosis) and pathological changes (hypodensities) in the third metacarpal/metatarsal bones, first phalanx, and proximal sesamoids whilst correlating these findings with training records and clinical assessments including lameness and joint effusion. Each additional furlong of high-speed work significantly increased both subchondral sclerosis and the incidence of pathological bone lesions, with joint effusion emerging as a sensitive clinical marker of these structural changes—notably, lameness itself was not associated with the observed bone pathology. The findings suggest that bone remodelling occurs silently during early training, ahead of clinical lameness presentation, and that joint effusion may warrant closer investigation as an early warning sign of cumulative training stress rather than dismissed as benign. For practitioners managing young racehorses, this work underscores the importance of monitoring high-speed mileage accumulation and joint fluid changes during the crucial conditioning phase, as radiographically silent subchondral damage may predispose to the catastrophic fractures that claim young horses under racing stress.
Read the full abstract on PubMed
Practical Takeaways
- •High-speed training in young Thoroughbreds (2-year-olds) accumulates subchondral bone damage that may not present as lameness; joint effusion is a more reliable clinical indicator of ongoing bone pathology than lameness alone
- •Progressive increases in racing workload correlate with measurable bone sclerosis and pathology on CBCT; trainers and veterinarians should consider monitoring cumulative high-speed furlongs alongside joint ultrasound for early detection
- •Standing CBCT may be a valuable screening tool to identify subclinical subchondral bone damage before catastrophic injury, particularly in young racehorses beginning high-speed training
Key Findings
- •Subchondral bone sclerosis increased significantly with accumulated high-speed furlongs (coefficient = 0.45; p < 0.003)
- •Subchondral bone pathology increased significantly with high-speed exercise (IRR = 1.01; p < 0.001)
- •Joint effusion was associated with both sclerosis (IRR = 1.01; p = 0.02) and pathology lesions (IRR = 1.14; p < 0.01)
- •Lameness was not associated with subchondral bone sclerosis or pathology despite imaging changes