What are the early symptoms of osteosarcoma in dogs?

Many dog owners first notice something’s off when their pup hesitates to jump into the car or skip up the stairs—movements they once did without a second thought. This subtle reluctance, often brushed off as “just getting older,” can be one of the first signs of osteosarcoma, a painful bone cancer that’s especially common in large breeds like Great Danes or Labradors. You might also catch your dog limping after a walk, but unlike a temporary strain from chasing a squirrel, this limp doesn’t get better with rest and might even worsen over a few days.

Another red flag is swelling or tenderness in one of your dog’s legs. If you gently touch the area and your dog flinches, whines, or pulls away—even if there’s no visible cut or bruise—it’s time to pay attention. Some owners mistake this for a sprain from rough play at the dog park, but osteosarcoma-related swelling often feels firm and doesn’t go down with ice or over-the-counter pain relievers. Changes in behavior can also hint at trouble: a usually energetic dog might start napping more, refuse to play fetch, or even avoid being petted near a sore leg, all because they’re trying to hide their pain.

It’s crucial to act fast not just for your dog’s comfort, but also to stay compliant with local pet welfare laws. In most U.S. states and European countries, owners are legally required to provide adequate veterinary care for sick or injured pets, and delaying treatment for a condition like osteosarcoma could be considered neglect. For example, in California, the Animal Welfare Act mandates that owners address “serious health issues” promptly, and in the UK, the Animal Welfare Act 2006 requires ensuring a pet’s “need to be protected from pain, suffering, injury and disease.” A vet can run tests like X-rays or blood work to confirm a diagnosis, and early intervention—whether it’s surgery, chemotherapy, or pain management—can significantly improve your dog’s quality of life.

Keep in mind that osteosarcoma doesn’t just affect older dogs; some middle-aged pups can develop it too, especially if they’re large or giant breeds. That’s why it’s smart to make regular vet checkups part of your routine—many vets can spot early signs during a physical exam that you might miss at home. For instance, during a yearly visit, a vet might notice slight swelling in your dog’s leg that you didn’t see because your dog only shows discomfort when moving a certain way. Also, if your dog has a history of bone injuries or is on a diet high in certain supplements, your vet might recommend more frequent screenings, as these factors can slightly increase the risk.

Don’t let the fear of a tough diagnosis stop you from seeking help. The earlier you catch osteosarcoma, the more options you’ll have to keep your dog happy and comfortable. Whether it’s adjusting their daily routine to be easier on their sore leg—like switching to shorter, slower walks—or working with a vet to find the right treatment plan, every step you take makes a difference. And by staying on top of their health, you’re not just being a caring owner—you’re also following the law and setting a good example for other pet parents in your community. Remember, your dog can’t tell you when they’re hurting, so it’s up to you to watch for those small, early signs that something’s wrong.