Has he got a limp? If so, it’s his nod I keep an eye on
When people hear about ‘nodding dogs’, most have a mental image of a small toy dog sitting on the back shelf of a car, with its head bobbing gently as the car moves.
In the veterinary world, a dog’s nod can be a useful diagnostic tool when assessing a lame animal. A recent case of a complex lameness in a dog provides a good example.
Tiger is a boisterous nineyear-old terrier who started to limp when out on walks.
He loves exercise, charging everywhere at top speed, but it became obvious that he was walking unevenly when he got tired. His owner found it difficult to say which leg was bothering him, but he was definitely not walking normally. He was brought in to see me so that this could be checked out.
I started by watching Tiger walk up and down in the corridor outside my consulting room. Normally when a dog is lame, you can spot the painful leg by watching them carefully while they walk. When you analyse the irregular movement of a limping dog, the most obvious abnormality is actually the movements of the head, rather than anything specific about the leg itself. A lame dog nods its head up and down far more than normal.
You can mimic this yourself, by pretending that you have a limp as you walk around the room. You’ ll soon discover that you naturally lift your head up as you try to avoid putting weight on the leg that you’re imagining is painful. And then when you put weight on your ‘normal’ leg, you’ ll find that your head nods down low. So if someone was watching you hobble around, they’d see your head lifting on the lame leg, then dipping down low on your good leg.
This same sequence of events happens with a lame dog, but there are two complications. First, the lameness is sometimes so subtle that the nodding of the head can be difficult to see clearly; it’s more of a twitch than a full scale nod. And second, the dog is often walking so rapidly that it’s difficult to identify the precise point at which the head goes up or down.
This is how it was with Tiger: as he rushed down the corridor with enthusiasm, I could see that he was lame, but it was difficult to be precise abut the exact timing of the subtly abnormal movements of his head.
I decided that it would be easiest just to examine him, flexing and extending each joint of both of his front legs. The painful joint would soon become obvious.
In fact, it turned out to be more complicated that I’d expected. Tiger is a terrier with bowed front legs: both front feet splay outwards at the equivalent of his wrists. This is common in many terriers, and it doesn’t cause them serious problems. It does, however, make the anatomy of their front legs more difficult to assess.
I remember a lecture at vet college when the speaker put up slides showing xrays of a dog’s front legs. He asked us what was wrong with the dog. We could all tell that there was something amiss, because the bones looked so different to the standard X-rays that we’d been studying up till then. The correct answer amazed us: the x-rays had been taken from a perfectly normal Bassett Hound. There are some breeds and types of dogs that are ‘normally abnormal’, and this makes it difficult when you are searching for the cause of a lameness.
Tiger was such a dog. His right wrist didn’t flex in the normal way at all, and although it wasn’t very painful, it was definitely not normal. But was this just the way Tiger had always been? Meanwhile, he was a wriggly dog who became restless when he was being poked and prodded. It was difficult to examine all of his joints closely, carefully and calmly.
My best guess was that he might have sprained his right wrist, so I gave him treatment to help this, with pain relief and rest.
When he was still limping a few weeks later, it was time to get more specific.
This time, I was determined to sort out precisely which leg was lame. I gave him a gentle sedative so that he was no longer straining enthusiastically at the leash. I then took a video of him calmly walking down the corridor. When I replayed the video in slow motion, there was no doubt about it: his head nodded down when his right foot hit the ground, and lifted up when his left foot was bearing weight. He definitely had a left forelimb lameness.
Then, while he was still sedated, I examined each of the joints of his left leg in detail, starting with his toes and working up the limb. If he had been fully awake, this would have been impossible to interpret: he would have been leaping and yelping during the entire examination. However, with the sedation to slow him down, it was much easier: he only yelped once, when I moved his left shoulder joint in a specific direction. So now I knew for sure: the source of his pain was his left shoulder.
X-rays were needed to solve the final piece of this jigsaw puzzle. These confirmed the cause of his lameness: he had signs of arthritis in his shoulder joint. He’s been treated for this now, with a combination of anti-inflammatory drugs and medication to improve the health of his joints.
I expect that Tiger will soon be walking normally, with no visible nodding or lameness. Mind you, he’s such a fast mover that I’ ll need a slow motion video to confirm that he’s better!