Joint cancer, also commonly referred to as cancerous arthritis, is a condition in which abnormal cell growth occurs in the tissues of the joint, resulting in a tumor. Joint cancer is commonly malignant rather than benign and generally spreads to other systems through the bloodstream. Arthritic cancer can occur in any joint in the body, and can be difficult to treat. It is likely to regrow even after surgical removal, and it responds poorly to common cancer treatments like chemotherapy. If the cancer is identified early on, before it can spread, the chances of survival are increased considerably. If your pet is demonstrating symptoms of joint cancer, contact your veterinarian immediately.

The primary symptoms associated with joint cancer closely mimic arthritis and include pain, inflammation, and loss of mobility or lameness. Joint cancer is very likely to spread through and can affect other parts of the body, including vital organs. As the cancer spreads, additional symptoms may be observed. In a significant number of cases, this type of cancer spreads to the lungs, causing lung-related issues. 

Symptoms Include:

Although synovial cell sarcoma is the most common type of joint cancer, other cancers can be found in the joints and surrounding tissues. Some of the types that can cause cancerous arthritis include:

Joint cancer, like all cancers, is caused by abnormal cell growth. In both benign and malignant joint cancers, this abnormal cell growth causes tumors in the joint and surrounding tissues. The specific cause of joint cancer has not been determined. Studies suggest that a combination of factors can contribute to the likelihood that joint cancer will occur. Risk factors include previous injury to the joint or bone, severe viral infections like feline leukemia virus or feline immunodeficiency virus, and abnormal joint development. Arthritic cancer is more common in older cats and affects males of the species more commonly than females.

Diagnosing joint cancer will require several methods of testing and analysis. The symptoms that point to joint cancer are very similar to non-cancerous arthritis and infections of the joint or bones, so your veterinarian will rely on a differential diagnosis that rules out other potential issues. Provide your veterinarian with the details of your pet’s medical history and any symptoms you have observed. A full physical examination will be completed to look for signs or injury or trauma that could be causing the limping or lameness the cat is experiencing. In some cases, a mass in the joint can be felt by veterinary staff during the physical examination. Analysis of blood and urine samples will also be completed to rule out infections and other issues. 

If cancer is suspected, x-rays or other imaging techniques like ultrasounds or CT scans will be completed to locate the cancerous growth and determine which portions of the animal’s body have been affected. In addition to using imaging to look at the joints, veterinary staff will also look at the lungs and abdomen for signs the cancer has spread. If a mass is observed, a biopsy will be completed to identify the nature of the cancerous growth and determine if it is benign or malignant. A needle or surgical biopsy may be completed. Additionally, fluid may be removed from the joint for analysis. This is generally completed with a needle. These methods will allow your veterinarian to diagnose joint cancer, its severity, and identify the staging.

Joint cancer generally requires surgical intervention, and amputation of the limb is the most commonly prescribed method of treatment. Cancerous arthritis responds poorly to other treatment methods and is very likely to reappear even after surgical intervention. Treatment may not be a viable option if the cancer has spread or is late-stage. Some common treatment methods include:

Complete surgical removal of the affected limb is the most common and successful treatment method for joint cancer. This treatment requires the cat be hospitalized and placed under anesthesia for surgery. This carries a moderate risk, as does any surgery. Your pet will be hospitalized for a few days to weeks to ensure proper healing. Lifestyle changes may also be necessary while your pet adjusts to life without its limb. 

In cases with smaller tumors, surgery to remove the affected cells may be recommended. This treatment also requires anesthesia and carries a moderate risk. Surgery is generally performed on an inpatient basis and may require one or more days of hospitalization. 

Joint cancer has proven difficult to treat with chemotherapy alone. This treatment method is more commonly used in conjunction with surgical intervention. It carries a low to moderate risk of side effects, with the most common side effect being lethargy and a weakened immune system. 

Your pet’s prognosis will depend on the severity, staging, and spread of joint cancer. The earlier the cancer is caught and treated the greater the likelihood the cat will recover. If a limb is amputated, your pet may need additional support while adjusting to life without their limb. It is possible for your cat to live a full life after amputation. While they are healing, make sure that their food, water, and litter are kept nearby. Notify your veterinarian immediately if symptoms return or worsen. Regular check-ups to watch for recurrence of cancer in the joints will also be needed.