Sudden Conformation Change in an Aged Mare

Q. I have a 20-year-old Dutch Warmblood mare that I have owned since she was born. She has been in extensive training and showing since she was four and has been awarded high honors in breeding quality status. However, over the past two years she has become increasingly over at the knee and bobbles her knees just standing in her stall.

She fell down while I was riding her not long ago in a very freakish manner. In all the years of training and showing her this has never happened. I’m hoping you can explain what causes a horse to be over at the knee, and why does she have this issue now when she had excellent conformation growing up? Could it just be old age? And if it is old age, what is mechanically happening? Might she be in the early stages of Cushing’s? Why, at 20 years old, has she has developed this fault?

—Julie, via email

A. You have obviously thought a lot about possible reasons for your mare’s acquired conformation, and you have, in fact, covered most of them. Because you did not mention any episodes of obvious lameness, I will assume that your mare is not responding to the presence of any chronic orthopedic pain. This is, however, an assumption on my part. You also did not mention if there has been a change in her farrier and/or in the trimming or shoeing of her feet. Again, I will assume that she is properly trimmed/shod and has been so consistently.

It is hard to know the significance of her one-time episode of falling down. Any number of things might explain this, so I would not make too much of it at this time. That said, I would also advise that she not be ridden until you gain a better understanding of her problem.

While faulty skeletal conformation can result in an “over at the knees” appearance, that is an explanation for this problem in a young horse. Certainly your mare is in the “at-risk” age group for equine Cushing’s disease (or pituitary pars intermedia dysfunction), and it is wise of you to have her tested. Many Cushingoid horses acquire a dull, unenergetic presentation and give the impression of muscle fatigue or weakness. This could be one reason for her to lack the strength necessary to brace her legs while standing. As a member of a heavier breed, the possibility of abnormal muscle metabolism exists. Finally, the presence of subtle neurologic dysfunction should be considered.

If your mare has not had a thorough physical examination within the past six months, I would suggest that you schedule one as soon as you learn the results of her Cushing’s disease test. Be sure your veterinarian is aware of your specific concerns so that all reasonable possibilities may be considered, including any additional laboratory testing.