Understanding the Stages of Arthritis in Dogs

Why Early Recognition Can Change Your Dog's Future

By Dr. Lisa Mason, DVM, CCRT, CVA, CVPP

If you've ever said, "I think my dog is just getting older," you're not alone. It's one of the most common things I hear from pet owners, and it's often said with the best of intentions. We expect our dogs to slow down as they age, sleep a little more, hesitate before jumping into the car, or take a few extra seconds to get up after a nap.

But here's what I want every dog owner to know: slowing down isn't always a normal part of aging—it can be one of the earliest signs of osteoarthritis.

Arthritis is one of the most common chronic diseases affecting dogs, yet it's also one of the most underrecognized. Studies suggest that approximately one in five adult dogs has osteoarthritis, and that number increases dramatically as dogs get older. Even more surprising, research has shown that many dogs begin developing arthritic changes long before their owners notice a limp or obvious signs of pain.

Unlike people, dogs rarely cry out or complain when something hurts. Instead, they adapt. They shift their weight to healthier limbs, shorten their stride, avoid certain activities, or simply become less active. Because these changes happen gradually, they're often mistaken for "just getting older."

As a veterinary expert in rehabilitation and pain management, I see the effects of arthritis every day. I also see something incredibly encouraging: dogs do not have to live with chronic pain. When arthritis is recognized early and managed appropriately, we can often reduce pain, improve mobility, maintain muscle strength, and help dogs continue doing the things they love for years to come.

One of the biggest advances in veterinary medicine has been recognizing that arthritis is not an all-or-nothing disease. It's a progressive condition that develops over time, and there are opportunities to intervene at every stage. We no longer wait until a dog has severe arthritis before recommending treatment. Instead, our goal is to identify dogs at risk, recognize the earliest signs of disease, and build a personalized plan that supports lifelong joint health.

To help veterinarians and pet owners better understand where a dog falls along that journey, we often use the Canine Osteoarthritis Staging Tool (COAST). Rather than simply labeling a dog as "arthritic" or "not arthritic," COAST divides the disease into stages based on risk factors, clinical signs, examination findings, and diagnostic imaging. This allows us to recommend treatments that are appropriate for your dog's current stage while helping slow the progression of the disease.

In this guide, I'll walk you through each stage of canine osteoarthritis—from dogs that are simply at higher risk to those living with advanced arthritis. We'll discuss what changes you might notice at home, how veterinarians diagnose arthritis, and the many treatment options available today. We'll also explore why rehabilitation, weight management, exercise, medications, and other therapies work best when used together as part of a comprehensive, individualized treatment plan.

Whether your dog is a young Labrador recovering from a cruciate injury, an active sporting dog beginning to show stiffness, or a beloved senior companion who struggles to get up each morning, understanding the stages of arthritis is the first step toward helping them live a more comfortable, active life.

The good news is that arthritis doesn't have to define your dog's future. With early recognition, thoughtful treatment, and ongoing partnership between your family veterinarian and a rehabilitation team, we can often help dogs stay mobile, comfortable, and engaged in the activities they love.

Let's begin by looking at what arthritis actually is—and why it develops in the first place.

What Is Osteoarthritis?

When most people think of arthritis, they picture "bone rubbing on bone." While that can happen in advanced cases, it's actually a very simplified—and often misleading—description of what osteoarthritis really is.

Osteoarthritis (OA) is a lifelong, progressive disease that affects the entire joint—not just the cartilage. It involves ongoing inflammation and changes to the cartilage, bone, joint lining (synovium), ligaments, joint capsule, and surrounding muscles. Over time, these changes can lead to pain, stiffness, reduced mobility, and loss of function.

In a healthy joint, cartilage provides a smooth, cushioned surface that allows bones to glide effortlessly during movement. Synovial fluid lubricates the joint, while strong muscles and ligaments provide stability and support. Every part of the joint works together to create comfortable, efficient movement.

When osteoarthritis develops, that balance begins to change.

The disease often starts with inflammation inside the joint. This inflammation triggers a cascade of events that gradually damages cartilage, alters the underlying bone, thickens the joint capsule, and weakens the muscles surrounding the joint. As muscles become weaker, the joint becomes less stable, placing even more stress on the tissues and creating a cycle of pain, inflammation, and further degeneration.

One of the biggest misconceptions about arthritis is that it happens suddenly. In reality, arthritis develops over months or even years. Long before a dog begins limping, subtle changes are already occurring inside the joint. This is why we place so much emphasis on recognizing the earliest signs of disease rather than waiting until arthritis becomes severe.

What Causes Osteoarthritis?

There isn't just one cause of osteoarthritis. Instead, it's usually the result of a combination of factors that place abnormal stress on a joint over time.

Common causes include:

• Developmental orthopedic conditions such as hip dysplasia, elbow dysplasia, or osteochondritis dissecans (OCD)

• Cruciate ligament injuries, including partial or complete tears

• Luxating patellas

• Previous fractures or joint trauma

• Repetitive athletic stress in sporting or working dogs

• Excess body weight

• Age-related wear combined with a lifetime of joint use

• Genetics and breed predisposition

Some dogs are simply born with joints that don't develop normally. Others experience an injury that changes the way a joint functions. Even after successful surgery, those joints often remain at increased risk for developing osteoarthritis later in life. That's one of the reasons rehabilitation plays such an important role—not just in recovery, but in protecting long-term joint health.

Arthritis Is More Than Pain

While pain is certainly one consequence of osteoarthritis, it isn't the only problem we worry about.

Pain causes dogs to move less. Reduced activity leads to muscle loss, decreased flexibility, poor balance, weight gain, and reduced cardiovascular fitness. Those changes place additional stress on already painful joints, making movement even more difficult.

This creates what I often describe to owners as a downward spiral:

A sore joint leads to less activity.

Less activity leads to weaker muscles.

Weaker muscles provide less support for the joint.

The joint becomes more painful.

The dog becomes even less active.

Without intervention, that cycle tends to continue.

The encouraging news is that we can also create the opposite effect.

When we reduce pain and improve movement through a comprehensive treatment plan—including rehabilitation, weight management, appropriate medications, therapeutic exercise, and other supportive therapies—dogs become more active. Increased activity helps rebuild muscle, improve joint stability, and maintain mobility, creating a positive cycle that supports long-term function.

Arthritis Is a Disease We Manage—Not One We Cure

One of the most important conversations I have with pet owners is about expectations.

Currently, there is no cure for osteoarthritis. We cannot reverse cartilage damage or return an arthritic joint to its original state. However, that does not mean nothing can be done.

Today's treatment options are better than ever before. Our goal is to slow disease progression, reduce pain, improve mobility, preserve muscle mass, and help dogs continue enjoying the activities that make life meaningful.

Every dog is different, which is why there is rarely a single "best" treatment. Instead, we use a multimodal approach, combining therapies that address different aspects of the disease. This may include rehabilitation, weight management, therapeutic exercise, medications such as NSAIDs or Librela®, injectable therapies like Adequan®, acupuncture, laser therapy, shockwave therapy, joint injections, and home modifications tailored to your dog's individual needs.

The earlier we begin that journey, the greater our opportunity to make a lasting difference.

That's why understanding where your dog is along the arthritis spectrum is so important. Rather than viewing arthritis as something a dog either has or doesn't have, we now recognize that it develops in stages—and each stage presents an opportunity to intervene before more damage occurs.

What Is COAST Staging?

If you've ever been told your dog "has arthritis," you may have wondered what that actually means. Is it mild? Advanced? Is there anything you can do to slow it down?

Until recently, veterinary medicine didn't have a standardized way to answer those questions. Dogs were often simply described as "arthritic," even though the disease can range from subtle joint changes with no obvious symptoms to severe pain and loss of mobility.

That's where the Canine Osteoarthritis Staging Tool (COAST) comes in.

COAST is an internationally recognized system developed by veterinary experts to help identify, classify, and monitor osteoarthritis throughout a dog's lifetime. Rather than viewing arthritis as a disease that suddenly appears, COAST recognizes that it develops gradually and progresses through several stages.

One of the reasons I appreciate the COAST system is that it changes the conversation from "Does my dog have arthritis?" to "Where is my dog on the arthritis journey, and what should we be doing now?"

That shift is incredibly important because every stage presents an opportunity to help your dog.

Looking Beyond X-rays

Many people assume arthritis is diagnosed only with X-rays, but the reality is much more comprehensive.

COAST considers several pieces of information together, including:

• Your dog's age, breed, and lifestyle

• Previous orthopedic injuries or surgeries

• Your observations at home

• Physical examination findings

• Muscle condition and gait

• Joint mobility and pain

• Diagnostic imaging, when appropriate

As veterinarians, we often learn just as much from your observations at home as we do from what we see during the examination. Changes such as hesitating before jumping, slowing down on walks, or becoming less interested in playing fetch may be some of the earliest clues that arthritis is developing—even before significant changes appear on X-rays.

The Five COAST Stages

COAST divides dogs into five stages, beginning before arthritis is even present.

Stage 0 – At Risk

These dogs don't have arthritis, but they have risk factors that make future joint disease more likely. This may include breeds predisposed to hip or elbow dysplasia, dogs recovering from a cruciate ligament injury, overweight dogs, or highly athletic dogs that place repetitive stress on their joints.

This stage is all about prevention. Maintaining a healthy body weight, staying physically fit, and addressing orthopedic problems early can significantly influence long-term joint health.

Stage 1 – Mild Osteoarthritis

At this stage, arthritis has begun, but signs may be very subtle. Owners often notice occasional stiffness after resting, slight hesitation with stairs or jumping, or reduced endurance during exercise. Many dogs still appear happy and active, making these early changes easy to dismiss.

This is often where we have our greatest opportunity to slow progression.

Stage 2 – Moderate Osteoarthritis

Dogs with Stage 2 arthritis typically show more consistent signs of discomfort. They may limp after activity, struggle to rise from lying down, lose muscle mass, or avoid activities they once enjoyed. Pain becomes more noticeable, and treatment usually requires a more comprehensive approach.

Stage 3 – Severe Osteoarthritis

At this stage, arthritis significantly affects a dog's daily life. Mobility becomes increasingly limited, pain is more persistent, and muscle loss is often substantial. Dogs may need assistance getting up, climbing stairs, or getting into the car. A multimodal treatment plan becomes essential to maintain comfort and function.

Stage 4 – End-Stage Osteoarthritis

Dogs with Stage 4 arthritis have advanced, debilitating joint disease that profoundly impacts their quality of life. Even simple activities such as standing, walking, or lying down comfortably may become difficult. While we cannot reverse the damage, compassionate pain management, rehabilitation, environmental modifications, and individualized care can still make a tremendous difference in helping these dogs remain comfortable and engaged with their families.

Why Staging Matters

One of the biggest misconceptions about arthritis is that treatment begins only when a dog is obviously painful.

In reality, the earlier we intervene, the better our chances of preserving joint function and slowing disease progression.

Think of arthritis like climbing a hill. The farther a dog progresses, the more difficult it becomes to regain lost mobility. If we can recognize the disease early—before severe cartilage damage, muscle loss, and chronic pain develop—we have many more tools available to help maintain an active, comfortable lifestyle.

That doesn't mean dogs with advanced arthritis can't improve. In fact, some of the most rewarding cases I see are senior dogs whose families believed "nothing more could be done." With thoughtful rehabilitation, effective pain management, weight optimization, and a personalized treatment plan, many of these dogs regain strength, confidence, and a better quality of life.

Staging Guides Treatment—Not Expectations

One of the things I appreciate most about the COAST system is that it reminds us to treat the individual dog, not just the stage.

Two dogs with the same radiographs may have very different levels of pain, muscle strength, activity, and lifestyle. One may be hiking every weekend, while another struggles to get off the couch. That's why every treatment plan should be individualized.

At Florida Veterinary Rehabilitation, COAST staging helps us create a roadmap for each patient. It allows us to recommend the right combination of rehabilitation, therapeutic exercise, weight management, medications, joint injections, regenerative therapies, acupuncture, laser therapy, shockwave therapy, home modifications, and ongoing monitoring based on where your dog is today—and where we want to keep them tomorrow.