Histopathologic features of distal tarsal joint cartilage and subchondral bone in ridden and pasture-exercised horses.

This study investigated if the exercise history and intensity in horses affects the condition of their distal tarsal joint cartilage and subchondral bone. Results suggested that high-intensity exercise, especially in competition horses, may increase the risk of osteochondral lesions, relative to low-intensity or non-ridden exercise.

Research Methodology

• The study involved 30 cadaver horses that did not have any lameness and had known exercise histories. These horses were separated into three groups based on their exercise levels: nonridden, pasture exercise (group P); low-intensity, ridden exercise (group L); and high-intensity, elite competition exercise (group E).
• The researchers prepared histological sections from standardized sites of the centrodistal and tarsometatarsal joints of these horses.
• They used a specific grading system to describe the location, depth and shape of the lesions, the arrangement of the cellular structure, the organization at the junctions of the cartilage and subchondral bone (SCB), and the structure of the SCB.
• A higher score on the grading system signified severe pathological changes. The scores were compared using the Spearman rank correlation calculation method to determine the relationship between exercise level and histopathologic characteristics.

Results and Findings

• In the centrodistal joint, lesions were found only on the medial side in both groups L and E. Cellular arrangement scores were higher at the dorsomedial location in group P compared to groups L and E.
• Groups L and E demonstrated higher scores for organization of cartilage, SCB junctions, and SCB, particularly at the dorsomedial location, compared to group P.
• In contrast, for the tarsometatarsal joint, lesions were spread across the entire joint surface in all three groups. However, the severity of the lesions was greater on the lateral side in all three groups.
• On the whole, group E (high-intensity, elite competition exercise) had higher scores for cellular arrangement and SCB organization compared to groups P (non-ridden, pasture exercise) and L (low-intensity, ridden exercise).

Conclusion

• The findings suggest that ridden exercises, specifically high-intensity ones prevalent in competitive horses, may increase the risk of osteochondral lesions at distal tarsal sites. This study points to a potential link between the intensity of exercise and the risk of osteoarthritis in horses.