Q: How does a vet diagnose navicular?

A: In recent years most vets have moved away from the term navicular syndrome, as it does not seem specific enough to describe what’s often going on in a case of lower-limb lameness. Navicular syndrome is classified by its degenerative impact to the navicular bone itself. This is usually too specific to describe the many number of reasons for lameness in the navicular area. There can be pathology in the navicular bursa, just below the navicular bone or soft tissue around the area such as the deep digital flexor tendon and the articulation point of the coffin, pastern and navicular bones for example. Today, you’re therefore more likely to hear vets discuss heel pain or caudal heel syndrome until the root cause can be narrowed down (it indeed it can).

There are a few approaches to pinpoint the exact area of concern in horses with caudal heel pain but most vets will start with a general soundness examination. This allows them to see your horse move on hard and soft ground and to gather information about his symptoms. Hoof testers are also useful in early diagnosis as almost all horses with navicular-area lameness will show sensitivity over the frog and heel.

Imaging, including X-Rays, MRIs and ultrasound have previously been common tools in diagnosis. However, the results can be inconclusive. It is not uncommon for an unsound horse to have clean imaging results and a perfectly sound horse to have irregularities on imaging. Imaging can be a helpful tool, thought, so shouldn’t be dismissed altogether. It just shouldn’t be the only approach.

Nerve blocks have become almost standard as diagnostic approaches. A palmar digital nerve block can show the extent of the lameness, with the vet applying local anaesthetic to the nerve of the lower pastern area in one leg. You’ll be able to see the difference between the sound and blocked leg due to the lack of sensation – this is assuming that unsoundness is experienced in two legs, which is most common. A peri-neural (around the nerve) or intra-articular (in the joint) anaesthesia may also be applied locally. Your vet will work their way up your horse’s leg, and when your horse trots off soundly, you’ve found the culprit, or at least the region of concern.

In essence, this is a quite a confusing area, and there isn’t a ‘one fits all’ diagnostic approach. Your vet is likely to need to perform a myriad of the above tests to find a specific cause, and unfortunately in many cases the exact issue may never be pinpointed. The good news is, however, that navicular no longer marks the end of the horse’s career in the vast majority of instances, with management practices and therapeutic agents improving all the time giving better and better outcomes for these horses.