We have investigated adaptive changes in the equine distal tarsal bones in response to exercise. Hocks from horses free from hindlimb lameness underwent MRI and microscopic evaluation. These were divided into 3 different groups: pasture exercise only, low-intensity exercise and high-intensity exercise. Sites from the centrodistal and tarsometatarsal joints were selected for examination. We found that subchondral bone and cartilage thickness increased with an increase in exercise intensity but maximal thickness was found in the medial aspect of the centrodistal joint and the lateral aspect of the tarsometatarsal joint in the high-intensity exercise group. We also found that joints from all 3 exercise groups showed evidence of osteoarthritis across the entire surface of the tarsometatarsal joint, but overall the horses in high-intensity work showed the most signs of osteoarthritis.
We recently published a study on MRI findings in the carpus and proximal metacarpal region of 50 lame horses. MRI enabled diagnosis of a variety of lesions not detected by conventional imaging in horses of a wide range of work disciplines. The distribution of injury types differed considerably from previous studies, which can be related to different populations or to the knowledge gained from our cadaver studies describing normal variations. The most common abnormality was mineralisation in the medial aspect of the carpal and metacarpal bones (n=28). Nine horses had syndesmopathy between the second and third metacarpal bones. In 6 horses the primary abnormalities were identified in the palmar cortex of the third metacarpal bone (McIII). Significant abnormalities of the suspensory ligament with associated lesions in the adjacent palmar cortex of the McIII were seen in 4 limbs. Ligament and associated osseous abnormalities between the second and third carpal bones and second and third metacarpal bones were detected in 4 limbs.
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