What is septic arthritis?

Septic arthritis is an infection in the joint fluid (also known as synovial fluid) and joint tissues. The infection usually reaches the joints though the bloodstream, although some joints may become infected after surgery or injury of an involved joint, which can expose the joint space to germs or infection.

In rare instances, an infection of the bone can spread to an adjacent joint causing septic arthritis. Bacteria, fungus, or viruses are capable of infecting the joint, although “septic arthritis” is typically used to describe non-viral causes of joint infections, which are usually caused by bacteria.

In most children, septic arthritis only affects one joint in the body. The most common sites for septic arthritis include the:

Knee
Hip
Ankle
Elbow
Wrist
Shoulder
Pelvis

Causes
Many different types of bacteria can cause septic arthritis. The type of bacteria depends on the site of infection, age of the patient, and any underlying medical conditions that may make a child more likely to acquire a joint infection.

Bacteria most often associated with septic arthritis include, but are not limited to:

Staphylococci
Haemophilus influenzae
Gram-negative bacilli
Streptococci
These bacteria can enter a child’s body in a variety of ways, including:

Infection that spreads from another source inside the body, such as a skin or bone infection adjacent to a joint
Infected wounds
Open fractures, or bones that penetrate through the skin
Foreign object penetrating the skin
Trauma
Signs and symptoms
Symptoms of septic arthritis vary from child to child and may differ depending on which joint is affected, the age of the child, and the type of organism causing the infection.

Septic arthritis typically has a fast onset with symptoms progressing to the point of severe pain and immobility of the affected joint within hours.

Common symptoms include:

Joint pain, usually severe
Joint swelling
Redness in the area of the affected joint
Warmth around the affected joint
Limping
Refusal to walk or bear weight on the affected joint
Limited use of the affected joint
Guarding or protecting the affected joint to prevent it from being touched or moved
Other symptoms of illness, such as fever, vomiting, sore throat or headache
Treatment
Specific treatment for septic arthritis will be determined by your child’s doctor based on:

Your child’s overall health and medical history
The type of bacteria causing the infection, location of infection, and predisposing medical conditions
Your child’s tolerance for specific medications, procedures, and therapies
Expectation for the course of the disease
Your opinion or preference
Septic arthritis usually requires treatment with antibiotics, which are often given intravenously to ensure prompt response to therapy. Antibiotics are only effective if your child’s condition is caused by a bacteria.

If your child’s infection is caused by fungi, he will need antifungal medications.

If a viral infection caused your child’s septic arthritis, the virus will usually need to run its course without treatment, although medications can be used to help alleviate pain.

In some cases, the infected joint must be drained and cleaned because antibiotics cannot penetrate deep enough into a severely infected joint. This may require drainage by a needle, tube or surgery.

Other symptom-based treatments may include:

Medications for pain and fever
Physical therapy to maintain muscle strength and joint range of motion
Splinting the joint to relieve pain

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