Septic Arthritis in Dogs

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What Is Septic Arthritis in Dogs?

Septic arthritis is an infection that occurs in a joint. Septic, in this context, means infected with harmful bacteria (most common), mycobacteria, fungi, or viruses. Arthritis is inflammation in the joint. Usually, septic arthritis occurs trauma, surgery, or a systemic infection in blood that travels to the joints.

Dogs with septic arthritis may quickly experience pain. As bacteria replicates in the joint, it leads to an inflammation that breaks down the joint. Early and often aggressive treatment is required to save the joints from chronic long-term damage.

Fortunately, septic arthritis is not contagious, though the bacteria that cause septic arthritis may potentially be contagious. While there are many species of bacteria, or even other agents, that can lead to septic arthritis, MRSA (methicillin-resistant Staphylococcus aureus) is one of the more contagious and dangerous agents that can spread from pet to pet, pet to human, or human to human.

Septic arthritis is rarely seen in dogs. Most that are affected with septic arthritis have had a penetrating injury to the joint, a recent orthopedic surgery where the joint was opened, or a suppressed immune system.

Septic arthritis is a medical emergency and should be immediately addressed. Early intervention is important to minimize joint damage.

Symptoms of Septic Arthritis in Dogs

Clinical signs of septic arthritis are both systemic—from the infection in the bloodstream—and local, from pain in the joint itself. The most common symptoms in dogs:

• Lameness or pain in one or more joints

• Heat or swelling in the joint

• Decreased or absent appetite

• Lethargy

• Fever

Causes of Septic Arthritis in Dogs

Septic arthritis is usually the result of a penetrating trauma, a complication of orthopedic surgery, or a systemic bacterial infection concentrated in the joint.

Dogs that have had a recent trauma, such as an animal bite over the joint or a puncture wound near the joint, are at greater risk of developing septic arthritis. All puncture wounds, especially if they’re near the joint, should be thoroughly cleaned.

Contact your veterinarian immediately if your dog has a puncture wound near the joint, as the vet may want to do additional flushing of the wound and prescribe antibiotics.

While sterile technique is always rigorously observed during orthopedic surgery in a dog, sometimes postoperative complications do occur. If your dog has had a recent orthopedic surgery, such as a ruptured cruciate ligament repaired or a bone plate or bone pin inserted, they have an inherent risk for developing an infection of the bone or joint after surgery.

Even the best surgeons using the best sterile technique in the best surgical suites cannot offer zero risk of postoperative infections. Airborne bacteria can still lead to an infected implant, and consequently, to an infected joint.

Diseases that suppress a dog’s immune system can increase a dog’s risk of developing septic arthritis. Additionally, there are cases of young animals spontaneously developing septic arthritis without trauma. Middle-aged, large-breed dogs have been documented to spontaneously develop septic arthritis in elbows that have underlying arthritic changes as well.

How Veterinarians Diagnose Septic Arthritis in Dogs

To diagnose septic arthritis, your veterinarian will start with a thorough physical exam. They will touch and examine any potentially affected joints and do a gait evaluation to assess for lameness. Heat or swelling of one or more joints is the most common clinical sign of septic arthritis. Your vet will also want to assess your dog’s overall state. Sometimes dogs with this condition will run a fever.

Your veterinarian will likely want to run some blood work to screen for signs that the infection is systemic (in the bloodstream). Additionally, x-rays are helpful to rule out other common underlying orthopedic conditions that can also affect the joint, like fractures. Some cases of septic arthritis can be accompanied by osteomyelitis, a bone infection. This often leads to changes to the underlying bone that are visible on x-rays.

After a physical exam, bloodwork, and x-rays, your veterinarian may want to do a procedure called arthrocentesis, also known as a joint aspiration or joint tap. This procedure involves using a sterile needle to collect joint fluid and cells to look at under the microscope. The fluid can also be sent off to a microbiology lab to culture for bacteria. Your dog will be given anesthetics to ensure that the procedure is pain-free.

If these tests do not provide answers, additional imaging like ultrasonography or a computed tomography (CT) scan may be recommended.

Treatment of Septic Arthritis in Dogs

Treatment of septic arthritis often involves aggressive therapy with antibiotics. If your dog is systemically ill and very sick when diagnosed, they may need to be hospitalized until they are stable. Sometimes these patients require lavage, or flushing with sterile saline, of the affected joints.

Often, patients with septic arthritis will be placed on oral antibiotics for a lengthy time. Follow-up visits to recheck the joints are recommended. Your veterinarian may need to repeat some of the previous diagnostics to ensure that the infection is resolving and that your dog is on the right track to recovery.

Monitor your pet closely while they’re undergoing treatment at home for septic arthritis. Note any changes in their comfort, gait, and appetite. Sometimes antibiotics can lead to gastrointestinal upset, so closely monitor your dog’s appetite and stools while on medication.

Follow the instructions on the label and do not discontinue an antibiotic prematurely unless instructed to do so by your veterinarian. Be sure to inform your veterinarian about any changes you notice in your dog’s response to treatment. Consider talking to your veterinarian about adding a probiotic while on antibiotics to keep a healthy gastrointestinal biome.

Recovery and Management of Septic Arthritis in Dogs

Your veterinarian may recommend rest while your dog is healing from septic arthritis. Be sure to ask about any activity restrictions. If your dog is not limping, low-impact exercise such as 15-minute slow walks is encouraged to maintain joint health. If your dog is still favoring, your veterinarian may recommend restricted activity to allow the joint time to rest.

Your veterinarian may prescribe an anti-inflammatory drug for your dog that helps ease pain and inflammation. Sometimes these medications can make dogs feel better and want to be more active than they should be during recovery. If your vet recommends your pet should rest, be sure to follow this recommendation even if your dog appears to feel better. Remember that their joint may not be healed yet, even though their pain is controlled.

Once your dog has been cleared to return to normal activity, physical therapy is geared toward a gradual return to full function and range of motion. Your veterinarian may recommend slow walks at first; you might start taking 10-minute walks and doing a slow serpentine pattern in the yard to strengthen the knees. Then, after a week or two of 10-minute walks, increase the walks to 15 minutes. Usually stairs, jumping, and running are the last activities to be added back in before your dog is back to normal.

Other physical therapy may include various range-of-motion exercises, such as moving your pet’s joints in a natural motion. A common exercise for the knees is moving the rear legs in a gentle circular motion, like pedaling a bicycle, while your pet is in a supported position. Your veterinarian is the best person to discuss a physical therapy plan for your dog, as plans will vary depending on the nature and severity of the infection, the age of the dog, and which joint(s) are involved.

Recovery times depend on:

• Severity of the joint infection

• Number and location of affected joint(s)

• Whether the infection is localized or systemic

• Time period between infection and start of treatment

• Individual response to therapy

Because so many factors can affect recovery time, it is difficult to predict duration. However, most patients can recover and return to full function in 4-12 weeks.

Most cases of septic arthritis are considered “cured” rather than just “managed” once they have resolved. However, having septic arthritis once does not mean your dog will never have it again.

Remember, if your dog sustains an injury that may involve the joint, be sure to get them appropriate care as soon as possible. If your dog has orthopedic surgery, follow all post-operative instructions and be open in your communication with your veterinarian to reduce your pet’s risk of post-operative complications.

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