Researchers at the University of Exeter in England have discovered that a significant number of horses have abnormal swelling in the bone marrow of their leg bones, called bone marrow oedema-like abnormalities (BMOA). These horses also had localized increased bone density. Drs. Christine Heales, Ian Summers, Jonathan Fulford, Karen Knapp and Peter Winlove say further research is needed to determine if the changes are associated with microdamage to the bones; several studies have linked micro-fractures to breakdowns in racehorses.
It is not understood what causes these abnormalities, which can be seen on MRIs. In humans, BMOAs unrelated to trauma are related to a range of issues, including diabetes, osteomyelitis and osteoarthritis, among others. BMOAs can also occur in people who begin a running regime; runners are more likely to have BMOAs than those who do not run; it's been suggested that these might be the early stages of a stress fracture.
The researchers used MRI scans on 65 distal metacarpal bones from the forelimbs of 43 horses, all with unknown histories. In total, 19 BMOAs were found. BMOAs locally increased bone density, suggesting that there was bone remodeling, but no measurable changes could be found. There were also no changes in the chemical composition of bone.
The researchers noted that the BMOAs were found in the region of bone that underwent the greatest loading; the site is commonly associated with lameness and injury in racehorses. They said it could be related to trauma even with no damage to the articular cartilage or evidence of microfractures present.
Further research is needed to determine if there is any association between BMOA and microfractures and bone remodeling.
Read more at HorseTalk.
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