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Sudden Onset (Septic) Arthritis in Cats: Signs & Care Guide (Vet Answer)

close up paw of a cat suffering from arthritis
Image Credit: C. Freshour, Shutterstock
Last Updated on November 16, 2023 by Dr. Iulia Mihai, DVM MSc (Vet)

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Written by

Dr. Iulia Mihai

Veterinarian, DVM MSc

The information is current and up-to-date in accordance with the latest veterinarian research.

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Arthritis is a condition that involves the inflammation of one or more joints. This name comes from the Greek words, “arthron” (joint) and “itis” (inflammation). There are many causes of arthritis in cats, and bacterial, viral, and fungal infections cause septic arthritis.

Cats suffering from septic arthritis usually present painful and warm joints, lameness, fever, loss of appetite, and lethargy. For your cat to maintain their mobility, you must get a timely diagnosis and ensure that your pet receives all the necessary care. If septic arthritis is left untreated, it can migrate to organs and lead to septicemia (sepsis), which can be fatal.

Keep reading to find out what septic arthritis is in cats, the causes and clinical signs, and how you can help your cat if they suffer from this condition.

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What Is Septic Arthritis in Cats?

Septic arthritis represents the inflammation and infection of one or more joints and their synovial (joint) fluid. It is caused by pathogenic organisms, such as bacteria, viruses, or fungi, that enter cats’ joints in various ways. This condition causes the destruction of the joint cartilage, which will vary depending on the virulence of the germs present in the joint.

The treatment of septic arthritis entails determining the type of microorganism involved and its sensitivity to antibiotics. Antibiotics are usually given for long periods. If the arthritis is caused by fungi, the veterinarian will prescribe antifungal medication to your cat. To help with your cat’s pain and inflammation, your vet will also prescribe anti-inflammatory medication along with the main treatment. Also, physical therapy may be needed for your cat to fully regain their mobility and speed up healing.

In some cases, surgery may be needed to drain the fluid from the cat’s infected joints.

hind legs of senior cat with arthritis
Image Credit: Roman Chekhovskoi, Shutterstock

What Are the Causes of Septic Arthritis in Cats?

Infection of the joints can be caused by sepsis (through the bloodstream) or by the direct penetration of germs into the joint in cases of trauma or bites. In other cases, septic arthritis can occur postoperatively, when the surgical site becomes superinfected.

Septic arthritis in cats is mainly caused by bacteria of the genus Pasteurella, which are commonly found in the throat (oropharynx) of cats and dogs. Other pathogens that can cause septic arthritis are:

  • Staphylococci
  • Streptococci
  • Bacteroides spp.
  • Coliform bacteria
  • Propionibacterium spp.
  • Fusobacterium spp.
  • Peptostreptococcus
  • Cryptococcus
  • Feline calicivirus
  • Mycoplasma
  • Leishmania
  • Blastomyces
  • Coccidioides

In very rare cases, septic arthritis can be caused by different species of ticks that transmit tick-borne diseases in cats, such as:

  • Rocky Mountain spotted fever (caused by Rickettsia spp.)
  • Ehrlichiosis (caused by Ehrlichia spp.)

Cats suffering from diabetes, pets with a weak immune system, or those undergoing treatment with medications that suppress the immune system are more prone to becoming ill.

What Are the Signs of Septic Arthritis in Cats?

Septic arthritis in cats has a sudden onset, unlike degenerative arthritis. The most common clinical signs are:

  1. Painful and inflamed joints
  2. Joints being warm to the touch
  3. Lameness
  4. Stiff joints
  5. Lethargy
  6. Malaise
  7. Lack of appetite
  8. Fever and depression (advanced cases)

When the primary infection is localized at the joint level, it can migrate to the organs and cause septicemia if left untreated.

cat with arthritis
Image Credit: Todorean Gabriel, Shutterstock

How to Care for a Cat With Septic Arthritis

When septic arthritis is diagnosed quickly (24–48 hours), antibiotic/antifungal therapy is effective in most cases. Therefore, follow the advice and indications of your veterinarian regarding your cat’s medication. You should also limit your cat’s movements until cleared by the vet.

To reduce your cat’s pain and inflammation, place cold compresses or ice packs over the painful area, alternating with heat packs. Never put ice or heat packs directly on your cat’s skin because you risk causing burns. Cover them with a towel to create a barrier.

When the treatment is delayed, your cat may experience joint degeneration and permanent damage. Also, in some cases, the infection could return, and your cat could develop septicemia.

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Septic arthritis represents the infection of one or more joints caused by bacteria (mainly), viruses, or fungi. This condition has a sudden onset, and the clinical signs include pain and inflammation at the joint level, lameness, warm joints, lethargy, fever, and lack of appetite. If your cat shows any of these signs, take them to the vet as soon as possible for diagnosis and treatment. To help your cat get over this issue faster, follow the veterinarian’s instructions and treatment. If your cat is in pain, apply cold compresses alternating with warm compresses over the painful joints.

Featured Image Credit: C. Freshour, Shutterstock

About the Author

Dr. Iulia Mihai, DVM MSc (Vet)
Dr. Iulia Mihai, DVM MSc (Vet)
Iulia Mihai is a veterinarian with over 13 years of experience in pet pathology, laboratory, and cancer. She studied at the University of Agronomical Sciences and Veterinary Medicine of Bucharest, Romania (EAEVE member), where she worked in the laboratory of the faculty clinic after graduation. She has a master’s degree in equine and pet pathology and studied epithelial cancer for her Ph.D. Iulia has a passion for internal medicine and parasitology and started volunteering at the faculty’s clinic in her third year of college. She has worked in a couple of veterinary clinics over the years as an internal medicine specialist. She enjoys writing and teaching people about cat nutrition, behavior, and disease prevention and treatment.

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