QUESTION from reader: Back in January 2020, my filly Ahlam (2018) (f) (Olympic Glory - Aksaray by Orpen) was due to go into pre-training in Ireland. The boarding stud noticed she was slightly lame behind.

The vet found bone chips in one hock, and then bone chips in the other hock. They operated to remove the chips, but on the last day of six weeks recovery (March 4th, 2020) Ahlam ran into a concrete wall at the vet clinic. She spent six months confined to her box at the boarding stud and never raced. I kept Ahlam for breeding.

In September 2024, my gelding Saint Eligius (2022) (g) (Recoletos - Ahlam by Olympic Glory) was in training in France. The trainer (Mathieu Brasme) told me he had been training well, was close to running in a race, but was hanging to the right. Saint Eligius had been in pre-training in France from November 2023 to the end of July 2024 before going to Mathieu Brasme.

I asked the trainer to have the vet x-ray the gelding’s four legs, as his mother Ahlam had bone chips when she was going into pre-training.They found a bone chip in the fetlock of Saint Eligius and last week they operated on him. The trainer could not remember which leg (left or right) and I never bothered to find out.

Saint Eligius will not run until 2025.

My topic for Horse Sense is Bone Chips in young horses.

  • Are bone chips common (statistics instead of guesswork)?
  • At what age are they likely to occur (age in months not years)?
  • Is it just a normal result of growth and bone formation?
  • What part of the leg is most commonly affected?
  • Are chips more frequent in front legs or in hind legs?
  • Any difference between colts, geldings, fillies?
  • Is it possible to take precautions to prevent them (e.g. postpone pre-training)?
  • Are they always treated by operation?
  • Do bone chips run in families (is genetics a factor)?

    • Answer: Our The Irish Field reader reported experiences with chips in a filly’s hock and thereafter the fetlock of her foal. Chips are often found under the stress of training when horses go lame or, more subtly, maybe hanging to one side or t’other. Joint blocks and ‘x-rays’ reveal a chip thought to be the cause.

    Even earlier, pre-sales/training radiography, as a common screening tool, sometimes shows up the presence of bony chips before the onset of any strenuous work or demonstrable clinical problem. Vets describe the underlying condition as osteochondrosis or OCD; sometimes using the phrase ‘developmental orthopaedic disease’ (DOD). Youngsters suffering from DOD develop a skeletal abnormality during a rapid growth phase, in particular if they grow excessively quickly and their diet is not ideal.

    It is important that people realise that the interpretation of radiographs is not an exact science. Chips can be confused with ‘normal variants’ – findings in a percentage of the population that are generally held to be of no clinical significance. These can look like chips associated with a joint, most notably the fetlock and hock, as our reader has experienced, but also knee, foot, pastern and neck. The reader asks about frequency – a difficult question to answer, as there are genetic components (nature), as well as management (nurture) elements.

    Thus, certain breeds e.g. warmbloods are at increased risk of DOD and certain blood-lines within a breed are further predisposed - so yes, DOD can run in families. The more closed is the studbook, the more closely-related are the horses in it; in-breeding concentrates bad traits, as well as the desirable traits (such as speed or jumping ability) that we seek; so closely-bred populations of horses suffer more.

    But, nutrition and foal growth before birth and during early life are significant factors too - one of the reasons why top-heavy, rapidly-growing colts are more often clinically affected than fillies. Never-the-less, all may harbour silent chips only found once someone goes looking or their offspring spring a problem.

    A silent chip may become a visible clinical issue following a traumatic event, e.g. a fall or getting cast, or from ‘normal’ exercise. Galloping causes pressure on soft young bones, particularly the front of knees; haut école dressage is stressful on hocks; landing steep from jumping high stretches the suspensory ligament, sometimes pulling bony fragments from behind the fetlock.

    BUT:

  • smooth, rounded ‘fragments’ may appear in these same locations in youngsters never yet asked to race or jump;
  • separate centres of ossification may be ‘normal variants’ present from birth and look like chips;
  • these may never become clinically significant

    • It’s not simple to distinguish between significant chips and incidental findings. If lame, blocking the joint with local anaesthetic may well help.

    A veterinarian may advise conservative management, especially if:

  • poor diet and rapid growth rate are felt to be key underlying causes,
  • time is not a major constraint but finances are,
  • the animal is not intended for public sale, at least until after achieving success.

    • But a veterinary surgeon (I use the phrase purposely!) may undertake surgery, if a chip can reasonably be labelled the cause of lameness or might likely excite future adverse comment – operating by the maxim ‘if in doubt, cut it out!’.

    Radiography and joint blocks help us to detect, understand and predict equine orthopaedic disease better; and then treat horses to help them to heal – which is what veterinary medicine is all about, when all is said and done.