Infectious Arthritis in Dogs

Infectious arthritis in dogs, which is also known as septic arthritis, is a type of arthritis that is caused by an infection in the fluid and tissues of a joint. It’s considered an inflammatory joint disease, unlike osteoarthritis which is classified as a degenerative joint disease. Inflammatory arthritis can affect either one joint or multiple joints, and it is usually recognized by signs of systemic illness such as fever, anorexia and stiffness in the limbs and joints.

Causes of Infectious Arthritis

Bacteria are one of the most common causes of infectious arthritis in dogs. Tick-borne diseases like Rocky Mountain Spotted Fever can introduce the bacteria that leads to infectious arthritis. Bacteria can also enter your dog's body through gum disease. Because of the connection between bacterial arthritis and gum disease, checking your dog’s teeth and gums regularly can be an effective way to avoid arthritis caused by infection. Viruses and fungal infections can also cause infectious arthritis but bacterial sources are the most widespread and also the most diverse.

Types of Bacterial Arthritis

• L-Form bacterial arthritis – L-form bacteria are bacteria that have no cell walls. This distinction makes them difficult to treat because certain antibodies, such as penicillin, are not effective because they work by attacking the cell walls of bacteria.
• Rickettsial arthritis - Rickettsial arthritis is contracted after being infected with rickettsia or rickettsia-like organisms through tick bites. Common tick-borne diseases that produce rickettsial arthritis are Rocky Mountain Spotted Fever and canine ehrlichiosis.
• Spirochetal arthritis - Spirochetal arthritis  is caused by sphirochetes, a spiral-shaped class of bacteria. This type of bacteria causes both Lyme disease and Relapsing Fever.

Viral Arthritis

A viral infection can occasionally cause a post-viral infection that results in joint pain because of the immune system attacking joints while in the process of fighting the invading virus. Considered a post-viral infection, this type of arthritis usually only lasts for about a week but could last longer, depending on the type of virus that caused the infection.

Fungal Arthritis

Fungal arthritis is a rare complication of a systemic fungal infection. Some of the most common fungi associated with this disease are:

• aspergillus terreus
• sporotrichum schenckii
• cryptococcus neoformans
• blastomyces dermatiditis
• coccidioidomycosis immitis

Symptoms of Infectious Arthritis

While infectious arthritis can affect multiple limbs, it usually affects only a single joint. Symptoms can include:

• swelling
• fever
• pain
• loss of appetite
• depression

Physical signs to watch for are:

• limping
• reluctance to walk or climb stairs
• difficulty rising from a resting position
• difficulty finding a comfortable resting position
• crying or whimpering for no apparent reason

Treating Infectious Arthritis

Infectious arthritis can be difficult to diagnose because clinical signs might not indicate a specific cause during the early stages of the disease. Proper treatment requires identifying the microorganisms involved so the proper antibiotics, anti-viral drugs, or anti-fungal drugs can be used.

Physical signs, joint fluid analysis, radiography, and microbiology testing are performed to determine both the type of arthritis and the treatment to be used. Arthroscopic surgery can also be performed to remove the infected synovial fluid and reduce the swelling and pressure on the joint.