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Signs of Osteosarcoma (Bone Cancer) in Dogs

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Lateral x-ray showing distal femur of a dog with osteosarcoma. Notice the large dark portion which is where the femur bone is being destroyed.

Lateral x-ray showing distal femur of a dog with osteosarcoma. Notice the large dark portion which is where the femur bone is being destroyed.

How Bone Cancer Affects Dogs

Osteosarcoma is a word derived from osteo, meaning bone, and sarcoma, meaning cancer. It's the cancer of the bones. It commonly strikes large dog breeds between middle age and the senior years, but it has been known to affect dogs as young as two. Osteosarcoma is less common in small dog breeds. Breeds particularly predisposed to osteosarcoma include:

  • Saint Bernards
  • Rottweilers
  • Great Danes
  • Golden Retrievers
  • Irish Setters
  • Doberman Pinschers
  • Labrador Retrievers

On average it affects dogs in the 7–7.5 year range. While it can affect basically any bone in the body, it typically affects the dog's legs (75–85% according to Mar Vista Vet). When a leg is affected, the condition is known as "appendicular osteosarcoma." Other predisposed areas include the ribs, vertebrae, and skull, yet bone cancer in these areas is rare. In this article, we will mostly tackle bone cancer of the limbs.

Dog osteosarcoma Codman triangle

Dog osteosarcoma Codman triangle

Pictures of Dog Legs Affected by Osteosarcoma

Signs of Osteosarcoma in Dogs

In osteosarcoma, the tumor originates from within the affected bone and destroys it from the inside out. The front limbs are most commonly affected, according to Vet Cancer Specialists. The cancer tends to form at or near the growth plates. The most common bones affected by osteosarcoma include, in order of preference:

  1. distal radius
  2. proximal humerus
  3. distal ulna
  4. distal femur
  5. proximal tibia
  6. distal tibia
  7. diaphyseal ulna

As vets often say, osteosarcoma in dogs is mostly seen “near the knee” and “away from the elbow.” See picture for exact locations of these bones. Sadly, dogs with osteosarcoma do not show symptoms in the early stages, which is why this condition is always discovered late and it is one of the most devastating diseases for dog owners to endure.

Progressive Lameness

Owners often report limping in a forelimb or hindlimb without an evident cause and that does not get better with time. The lameness may wax and wane for some time, generally several weeks, but will not go away. Generally, the limping goes from intermittent to constant over the course of 1-3 months. It gets gradually worse as the cancer damages the bone and causes pain for the dog. However, some dogs may be quite stoic and not clearly manifest pain. The lameness is triggered by inflammation of the membrane that covers the outer surface of all bone, microfractures, or pathologic fractures. It's always a good idea to routinely observe your dog's gait so you can readily recognize signs of trouble.

Often, vets will try to treat the lameness symptomatically before running further tests. When the vet will do an X-ray, the affected bone may show signs of destruction (lysis) or abnormal growth, as seen in a typical sunburst pattern or Codman's triangle, signaling that the periosteum has been raised due to the tumor. In some cases, a biopsy of the bone may be needed to obtain a definitive diagnosis.


As the cancer expands, it will cause swelling in the affected limb or shoulder area (see pictures). This swelling is therefore due to the expansion of the tumor into the surrounding soft tissues. The swollen area may appear hot to the touch and the dog may exhibit pain as the area is handled. However, as mentioned, the pain may not be that noticeable in stoic dogs. It's always a good idea to routinely touch your dog's legs and get familiar with how the bones and skin feel. If you ever feel a lump by the bone, or individualize a swollen joint, see your vet. If you are not sure, you can always use the other leg for comparison.


The affected dog's bone typically become eroded and is replaced by tumorous bone which is friable and prone to fractures that do not heal. Typically, the dog owner reports that the dog was playing one minute, and yelping the next when the fracture occurred. The fracture in this case is known as "a pathologic fracture" since it affects tumorous bone. X-rays of the bones may show eroded bones, the typical sunburst pattern or Codman triangle, which provide a diagnosis.

Difficulty Breathing/Coughing

Sadly by the time the cancer is discovered, almost 90% of cases have already metastasized, according to the American Kennel Club's Canine Health Foundation. Microscopic metastasis is therefore often present at the time of diagnosis. The most common area of metastasis are the lungs. This explains why your vet will often do a chest X-ray (2 lateral views and a ventrodorsal one) as well to check if the cancer has spread.

However, it appears that fewer than 10% of dogs show evidence of lung metastasis at the time of diagnosis, according to Vet Cancer Specialists. A CT scan of the lungs may be more effective than X-rays in identifying the initial small metastatic lesions. While metastasis to the lungs is the most common, other affected sites may be the liver, kidneys, amputation stump, and, nearby bones, even though rare.

Behavior Changes

When dealing with cancer, the dog's immune system is put to test which results in lethargy and tiredness. The dog may weaken and appear less interested in food. Pain may cause walks or play to be too much for the dog. Affected dogs may sleep more, appear tired and pain may put a big toll on the dog's quality of life. The dog with bone cancer may also appear grumpy and may not want to be touched. Amputation may make the pain more bearable, but will not cure the disease.

Occurrence of Bone Cancer in Dog Front Legs

In order of preference. Edited to show frequent bone cancer locations in dogs.

In order of preference. Edited to show frequent bone cancer locations in dogs.

A Grim Future for My Rotties?

Owning two Rottweilers puppies, I looked forward to getting them vaccinated and giving them a great head start in life by playing it safe and preventing any major disease or weakness by feeding the highest quality foods and having routine checkups all their lives. However, once they were six months old, I asked the vet when the best age was to get them neutered and spayed and her answer was as early as possible. I trusted my vet, and vets in general because I always thought of all the years of education they undergo. So I had them altered immediately a week thereafter. Big mistake...

Little did I know back then that there were studies out there suggesting that large breed dogs spayed and neutered too early in life were shown to be prone to osteosarcoma as they approached their middle to senior years! Actual studies have reported that chances of osteosarcoma decreased when Rotties were spayed and neutered once they were at least one year old. More precisely, the studies reported that male and female dogs spayed and neutered before 1 year of age had a higher incidence (1 in 4 chance ) of developing osteosarcoma!

This suggests that sex hormones play a role in the inhibition of bone cancer. Studies are currently underway to investigate the genetic susceptibility to osteosarcoma in Rottweilers and other breeds by fundings organized by the Canine Health Foundation and the Morris Animal Foundation.

Owning two Rotties, respectively spayed and neutered before one year of age, seems to make statistics quite scary for their future. So I have learned my hard lesson, and now I am always worried sick that one day or another one of my Rotts will start limping and showing signs of this devastating condition.

For Further Reading

  • Valley Fever in Dogs Coccidiomycosis
    Learn what is dog valley fever and how it affects your dog. Learn how this condition is treated and why it is important to have your dog seen immediately for any signs of this disease.
  • Dog Health: Signs and Symptoms of Dog Hip Dysplasia
    Learn the signs and symptoms of his dysplasia in dogs. Learn some effective strategies and products to make your dog's hip pain more bearable.
  • Treating Dog Torn Cruciate Ligament with No Surgery,...
    If your dog was diagnosed with a torn cruciate ligament, you may wonder if surgery is really necessary. Considerations and links to dog torn cruciate ligament non-surgical options.
  • Causes of Limping in Dogs
    Learn about some of the most common dog limping causes. Find out how to palpate the leg to pin-point problems and potential causes for front leg limping and rear leg limping in dogs.
  • Causes of Lumps on Dog Paw Pads
    Wondering what may cause unusual lumps and bumps on a dog's paw pad? Learn possible causes for why your dog has lump on paw pad and why it's so important to see the vet.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

Question: What's your opinion on amputation in osteosarcoma cases? It seems to delay the inevitable a few months.

Answer: Amputation removes the main source of pain so it offers quality of life. And dogs on three legs tend to do great, especially if it's the front leg to be amputated. Left untreated, the bone with the osteosarcoma will likely fracture (pathological fracture). Not all dogs are good candidates for the surgery, so this is something to discuss with a veterinary surgeon/veterinary oncologist.

© 2014 Adrienne Farricelli


Adrienne Farricelli (author) on September 07, 2020:

Hi Doni, so sorry your dog is going through this. It's heartbreaking when our best friends get old and sick. 14 is a very good age, every day is a blessing. No vet can force you to put a dog to sleep. I think a vet visit to see whether there are any pain meds that can give him a bit of relief may be helpful.

Doni Ramos on September 06, 2020:

My 14 year old queensland has lumps all over him one large one to he size of a cantelope off the side of his body and a very hard yet mushy on the top of his front paw and he has started eating and licking it I'm sure he is in pain but my spouse refuses to take him to vet because he thinks they will make him put him down he has been my shadow for the last 14yrs he watched my every move protected me and loved me no matter what and I want to do the same for him is it time to put him to sleep he is very over weight as well and my spouse thinks just because he gets happy to eat that he's not in pain but I disagree do you have any advice for me.

Adrienne Farricelli (author) on January 07, 2020:

Beth, so sorry you are going through this. Her low level of tolerance for pain certainly makes things harder. It may be worthy talking about this with your vet though as they sometimes can combine different types of pain meds which offer a synergistic effect. Sending you hugs at this difficult time!

Adrienne Farricelli (author) on January 07, 2020:

Carlos, so sorry for the loss of your beloved Rottweiler to this horrible form of bone cancer. Having owned Rotties myself, I know how they can steal your heart. They act stoic for as long as they can.

Beth on January 06, 2020:

My Pit was just diagnosed with Osteosarcoma. Her other front leg was injured as a pup, so amputation is out of the question. She already needs occasional NSAIDS for the other leg. She has no tolerance for pain whatsoever. I have a t-shirt that says In my darkest hour I reached for a hand and found a paw. Now I have to let that paw go before it really starts to hurt. I know the prognosis and what is to come. My heart is breaking, but I don't want her to suffer because I can't let go.

Carlos on October 30, 2018:

My best friend Rocco (9 year old Rottweiler) was diagnosed with osteosarcoma the summer of 2017. He started lipping his front left paw. At first I thought he stepped on glass or that he pulled a muscle. I brought him to the vet, and the veterinarian told me the heart breaking news. I didn’t want Rocco to get amputated and suffer since he weighed 115 pounds and was a senior dog. On October 29 2019 I made the decision to put him down. His wrist if you will, was the size of a soft ball. The vet proscribed him painkillers. He was such a tough dog. I loved him with all my heart. He gave me that look that he didn’t care for much activity. He wouldn’t get out of bed and really didn’t care for food . I know he’s not suffering anymore. It was the right thing to do. This is a terrible cancer.

R.I.P Rocco we love you!!!!

Meghan on October 01, 2018:

My sweet terrier mix Jack was diagnosed with Ostersarcoma this summer. We amputated his right front leg five weeks ago. It was a tough decision because he's 14 and the cancer is aggressive... but besides the painful leg, he was healthy and happy at the time. About a week ago, he started to change. He has a sad look in his eyes, he's really tired and his appetite has waned. I am so heartbroken to have put him through surgery for nothing. I just started him on I'm Yunity this morning. We decided against chemo because of his age and the side effects. This is a hail mary pass. I am hoping it will make him feel better so that we don't have to euthanize him right away. Has anyone else tried I'm Yunity? My vet recommended it. It's an immune booster that apparently can shrink tumors and increase appetite and energy levels.

Adrienne Farricelli (author) on July 12, 2018:

So sorry Ruth, this cancer is just so horrible.

Ruth on June 22, 2018:

Osteosarcoma is a nasty cancer. Our 10 yr old chocolat Lab Sadie had started licking her front leg a lot. We took her to vet in December 2017, Vet did not see anything. Two weeks later a knot appears on her front left leg below her bone plate; so back to the Vet we go. (She broke her leg before she was 1 year old....wished we knew about plates 9 years ago.) We had her front leg amputated in January and started chemo. She was doing fine up until about four weeks ago. We noticed her sleeping more, refusing to eat somethings and a reluctance to jump down off the bed, even with a steps. We took her to the Vet yesterday and Vet done x-rays of front leg and chest. Vet had a specialist look at x-rays and the cancer has now metastasized to her other front leg and a couple of nodules showed up in the lungs. My heart is breaking because I know now within the next couple of weeks I will be saying good bye to my best friend and companion......cancer @% #

Holle Abee from Georgia on March 07, 2018:

Adrienne, thank you for your kind words.

Adrienne Farricelli (author) on March 07, 2018:

Holle Abee, so sorry for your loss. Bone cancer is so mean. Rotties are also prone to it and so every time mine limp, I get worried and get them x-rayed to play it safe. Again, so sorry.

Holle Abee from Georgia on February 26, 2018:

Had to have my beloved Dane put down due to osteosarcoma. He was 8. The tumor was on his wrist. He never limped much, but he did have a slight decrease in appetite. Great Danes are prone to this terrible disease.

Atlas123456 on October 24, 2017:

Taking my Saint Bernard to the vet this Saturday. He has a lot of these symptoms. Not wanting to eat unless I add chicken to his food, seems very stiff when getting up, favors one rear leg over the other, walks slowly, sleeps more than usual. I hope it isn't cancer, he's only 6 years old. Just the thought is absolutely devastating.

Tina on June 05, 2017:

I just took one of my Rottie's yesterday to a new vet for limping and they did a 3D scan. They are sending it out for a second opinion but it doesn't look good for my sweet, sweet Maddie. Both her and her sister were spayed at 6 months by the advice of our previous vet. So sad to think my girl who has never been sick is going to have to be put down at the age of 8. I am already dealing with her sister having two disk issues and severe arthritis. Cancer sucks and to think of precious Maddie having it is devastating.

Adrienne Farricelli (author) on April 29, 2017:

Sarah, sending prayers your way.

Sarah on April 22, 2017:

My almost 14yr old 70lb large black lab Shepard mix started limping after being trampled by my other dog so I took her to the vet. We thought maybe a ligament or muscle (because X-rays showed no breaks) but after a week and a half her leg quickly got bigger and swollen.

I took her back to the vet today and I could tell when the vet tech left us in the room with just the dr, there was bad news. She had suspected osteosarcoma previously. She gave me antibiotics anyways because I'm hopeful it's just infected from a sore on her elbow. She is also taking tramadol and carprophen. I have had her since she was 8weeks and I was 15yrs, I'm heart broken.

Adrienne Farricelli (author) on February 24, 2017:

Benjamin, I am so sorry, bone cancer is so devastating.

Benjamin on February 23, 2017:

Im saying goodbye to my best friend of 9 and 1/2 years this weekend. We finally found out this past Monday that she had bone cancer on her left front leg at the wrist joint.

Adrienne Farricelli (author) on January 19, 2017:

NikkiB, so sorry to hear about your dog's bone cancer, it's really a devastating disease, to answer your question, there are some pet owners using it and indeed there is a Facebook page you may want join where people share their experiences.

NikkiB on January 18, 2017:

We adopted a 10 yo sharpei mix in mid-November, 2016. He was dx'd with osteosarcoma on Dec. 29, 2016. He'd become such a wonderful part of our family in those 6 weeks. We were told he had maybe 3 months. He is now on tramadol. He still eats well, he seems pretty happy other than limping. His tumor is on the humerus. In just three short weeks, we've already noted the progression of his tumor. It went from a "halved" golf ball size to a halved racquetball size in that short time. As long as he can get around, and wants to eat (and go for walks still!), we'll keep things as normal as possible.

I'm really curious- does anyone have any positive experience using cbd oil supplementation? I was hoping it might slow the progression down and ease his pain. Thanks!

Adrienne Farricelli (author) on November 29, 2016:

Rebecca, I am so sorry to hear about your dog. Just last week a client of mine had her dog diagnosed with bone cancer of the jaw, the symptoms were mimicking a bad tooth and then the x-rays showed the extent of the damage to the bone. Keeping you in my thoughts.

Rebecca Williams on November 29, 2016:

My 8 year old chocolate lab was just diagnosed. He started having seizures. After a MRI and biopsy it was confirmed. The growth is in his skull and growing toward his brain. Anti seizure meds are helping with the seizures, just don't know how much time he has. Very cruel disease.

Adrienne Farricelli (author) on September 25, 2016:

Karen, did your vet take x-rays of the leg and lungs? what about consulting with a veterinary oncologist?

Karen Phillips on September 25, 2016:

I'm pretty certain my beautiful gsd x has osteosarcoma in her back right leg. She was seem by a vet last week and we were told to go home and decide what course of action we would like to take. Amputation is not an option and it seems that putting her to sleep is going to be the result we are dreading. My heart is breaking at the thought of her leaving but more that she is and will continue to suffer. I'm looking at her sleeping peacefully at my feet and hoping that I can do what is right and best for her.

Adrienne Farricelli (author) on August 21, 2015:

Talk to your vet about amputation and chemo, I know many dogs who live happily more months or even years.

Debby on August 18, 2015:

Our Great Pyrenees dog Casper is being biopsy tested for osteosarcoma tomorrow. He is 7 yrs old. The sweetest guy you could imagine. It's pretty likely this will be bad news. All the signs are present. We just want to confirm our worst fears before we put him down. We had originally taken Casper to the vet because we thought he had a sprained leg. No clue this is what was going on. This is a very aggressive and quick cancer. Don't wait to take your large dog to the vet when he is limping. Get it checked out.

Devika Primić from Dubrovnik, Croatia on October 11, 2014:

A well-informed hub on this topic. Always something more from your writing about dogs and about their health issues.

Adrienne Farricelli (author) on October 10, 2014:

Goatfury, there are some cancers that can be treated at the early stages, or at least, managed for quite some time, but osteosarcoma is one of meanest, most painful, and with a poor prognosis and signs showing up when it's too late:(

Adrienne Farricelli (author) on October 10, 2014:

Heidithorne, that must have been devastating, what an awful disease. I hope those funded studies and research finally help shed some light on this cancer.

Andrew Smith from Richmond, VA on October 10, 2014:

Thanks for writing this. I really hope none of my dogs end up with osteosarcoma!

Heidi Thorne from Chicago Area on October 10, 2014:

We've had mutiple goldens with cancer. One of the most heartbreaking was my 2-year old who had osteosarcoma lodged behind his brain which then progressed into lymphoma. He had dramatic and early deterioration of his teeth. This also emphasizes the importance of canine dental monitoring and care to identify other health issues. Thanks for sharing the information!

Adry on October 09, 2014:

According to Pet Education: " Most osteosarcomas develop on the limbs of dogs below the elbow or near the knee". There are some that develop swelling in the shoulder area as you can see in the picture links, but hopefully in your dog's case it's something else. Definitively something that should be checked out by your vet though.

Susan Zutautas from Ontario, Canada on October 09, 2014:

My Newfoundland dog Bruce is 7 and will be 8 in March. He is not fixed. His right front leg where his elbow is, is quite swollen. He doesn't seem to be experiencing any pain except he is limping really bad. He started this about a week ago. After reading your hub I'm really worried. We had thought that maybe he had just pulled a muscle as he has had this happen a number of times in his life. I now think it would be best for us to take him to the vet.