Disjointed: What’s the difference between dysplasia and arthritis?


File photo. File photo.

A 9-year-old Rottweiler I’m examining is clearly having trouble lifting her hind end off the ground. And once she does, it’s obvious that she’d just as soon lie back down. It’s been getting worse for a few months, and I can see that the muscles of her rear legs are withering from disuse.

“I’m worried she’s getting hip dysplasia like my last dog,” offers the owner.

But it’s probably not hip dysplasia. And it probably wasn’t hip dysplasia with his last dog, either. How do I know? Because adult dogs don’t—and in fact can’t—suddenly just get hip dysplasia.

Hip dysplasia is a developmental disorder controlled largely by genetics; it appears very early in life, before animals finish growing. That means that a 9-year-old Rottweiler can’t develop hip dysplasia any more than she can become a Boston Terrier.

She can, however, develop arthritis, which is almost certainly the problem. The symptoms overlap, and the two diseases can interact to become a force greater than the sum of its parts.

Arthritis is the breakdown of the normal cartilage that cushions joints. It’s a response to physical stress, which is why we see it so commonly in older animals. Every clumsy landing and awkward fall gave that cartilage a good thump, and as the cartilage degrades, the joint becomes a rusty hinge with rough surfaces scraping against each other, limiting movement and causing pain.

So where does hip dysplasia fit into all this? The normal hip joint is smooth ball-in-socket model. Dysplasia turns the ball into a cube, and makes the socket too shallow to properly hold it. This mismatch causes stress on the poor joint, and now we know that a stressed joint develops arthritis. But since dysplasia is present from such a young age, the arthritis begins much earlier and has longer to worsen.

There are no easy options when managing a young dog diagnosed with hip dysplasia. Pain medication may help reduce symptoms, and low-impact exercise can strengthen the muscles surrounding the joint. Milder cases can do well for a while, but nothing changes the fact that you have a square peg in a round hole, and surgical correction is often advised.

Arthritis, on the other hand, is generally managed without surgery. Severely affected animals tend to be older, and the goal is usually to provide a good quality of life in their later years. We can help do that with medication, but it’s better to try and prevent our pets from ever needing that kind of intervention to begin with. Unlike dysplasia, which arises from genetic factors beyond an owner’s control, we can help our animals avoid arthritis with proper diet and exercise.

Nothing correlates better with arthritis than an animal’s weight. I can’t overemphasize how much you can improve your pet’s later years by keeping him trim in the earlier ones. Low-impact exercise like walking and swimming can burn calories while building muscle and protecting vulnerable joints from degeneration. You won’t prevent it completely, but you’ll slow it down, adding months (if not years) to your pet’s life.

There’s no question that hip dysplasia and arthritis have a lot in common, and recognizing the difference can help you better understand your own pets’ health and keep them more comfortable.

Dr. Mike Fietz is a small animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.