Foot pain is a frustrating lameness to diagnose. Until recently — unless laminitis with rotation, ringbone or navicular disease were evident on X-rays — the horse was likely to be undiagnosed.
The veterinarian would assume the horse had a bruise or would use a generic label like “tender footed” or “heel-pain syndrome.” What this really meant was yes, your horse’s feet hurt, but why, what to do and how to manage him were anyone’s guess.
Successful resolution of any lameness must begin with a diagnosis. Only then can a comprehensive plan for acute treatments, down time and rehab be formulated. “Tender footed” is not a diagnosis, and there’s no longer any reason to accept it.
Advances in diagnostic imaging now make the generic diagnosis largely a thing of the past — or at least it certainly should. Ultrasound has been around for a good while but now also is used to investigate the feet. MRI and bone scans are also providing more insight.
One of the most significant findings that has appeared through the use of these advanced diagnostic tools is that many foot-sore horses have problems involving the deep digital flexor tendon. Anyone who knows how hot, swollen and tender a bowed tendon in the upper leg is can easily imagine why a tendon injury enclosed inside the hoof would be painful.
A study performed at the Centre for Equine Studies at the Animal Health Trust in the United Kingdom, published in Equine Veterinary Journal, looked at 75 horses with foot pain confirmed by nerve blocks but without obvious cause on X-ray or by ultrasound examination.
Bone scanning and MRI showed that 61% of these horses had a significant lesion in their deep digital flexor tendon inside the foot, either in the body of the tendon itself or at sites where it inserted onto bone.
An additional enlightening observation was that palmar digital nerve blocks (heel nerves) eliminated the lameness in only 24% of these horses. The others took a combination of heel blocks and injection of anesthesia into either the navicular bursa area or the coffin joint itself to block sound. Some horses had only the flexor tendon abnormalities as a source of their pain, while others had tendon problems plus navicular area or other soft tissue (i.e. not bone related) problems.
What this tells us is:
• Negative X-rays and a failure to block sound with heel nerve blocks do not mean there is definitely no source of pain in the foot.
• If no improvement or only partial improvement with a heel block, moving on to coffin joint and navicular bursa anesthetic may confirm the foot as the source.
• Ultrasound may not pick up all soft tissue abnormalities so it’s worthwhile to move ahead with MRI or nuclear scanning at a full-service facility.