What is septic arthritis in children?

Septic arthritis is an infection in the joint fluid (synovial fluid) and joint tissues. It occurs more often in children than in adults. The infection usually reaches the joints through the bloodstream. In some cases, joints may become infected because of an injection, surgery, or injury.

What causes septic arthritis in a child?

Different types of bacteria, viruses, and fungi can infect a joint. The common types that can cause septic arthritis include:

• Staphylococcus aureus. These are common bacteria that often cause skin infections.

• Haemophilus influenzae. These are bacteria that can infect the larynx, trachea, and bronchi.

• Gram-negative bacilli. This is a group of bacteria that includes Escherichia coli (E. coli).

• Streptococci. This is a group of strep bacteria that can lead to many different diseases.

The most common type of bacteria that cause septic arthritis is Staphylococcus aureus (S. aureus or staph). These bacteria can enter the body in many ways, such as:

• An infection that spreads from another place on the body, such as the skin or genitals

• An infected wound

• A broken bone that goes through the skin (open fracture)

• Foreign object that goes through the skin

• Injury that breaks the skin

Which children are at risk for septic arthritis?

Septic arthritis may occur without any known risk factors. But children who have an open skin wound and a weakened immune system may be at greater risk. A weakened immune system can be caused by diabetes, kidney disease, HIV infection, cancer, immune deficiencies, or immunosuppressive medicines.

What are the symptoms of septic arthritis in a child?

The most common joints affected by septic arthritis are the knee, hip, shoulder, elbow, and wrist. Most often, only 1 joint is affected. Symptoms may vary in each child. Common symptoms include:

• Fever

• Joint pain, often severe

• Joint swelling

• Redness in the affected area

• Warmth around the affected area

• Limited use of the affected limb, such as not wanting to walk

• Guarding or protecting the affected area to keep it from being touched or seen

• Other symptoms of illness, such as vomiting, sore throat, or headache

• Being grouchy (irritable)

• Loss of appetite

These symptoms can seem like other health conditions. Make sure your child sees a healthcare provider for a diagnosis.

How is septic arthritis diagnosed in a child?

Early diagnosis of septic arthritis is important. It can prevent long-term (permanent) damage to the joint. Your child’s healthcare provider will ask about your child’s health history and give your child a physical exam. Tests may also be done, such as:

• Removal of joint fluid. This is done to check for white blood cells and bacteria in the fluid.

• Blood tests. These are done to look for bacteria.

• Phlegm, spinal fluid, and urine tests. These are done to look for bacteria and find the source of infection.

• X-ray. This test uses a small amount of radiation to make images of internal tissues, bones, and organs.

• Bone scan. This imaging test uses a tiny amount of a radioactive substance to look for arthritis changes in the joints.

• MRI. This test uses large magnets and a computer to make detailed images of organs and other tissues without using X-rays.

• Radionuclide scans. These scans use a tiny amount of a radioactive substance to look at organs and the blood flow to them.

How is septic arthritis treated in a child?

Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is.

Septic arthritis often needs treatment right away with antibiotics if bacteria are the source of infection. This can improve symptoms within 48 hours. Some infections caused by fungi need treatment with antifungal medicine. Viral infections are not treated with medicine.

Pus may be drained from the joint. Pus buildup can damage the joint. The pus is drained with a needle, tube, or surgery. Other treatment may include:

• Medicines for pain and fever

• Physical therapy to keep muscle strength

• A splint on the joint to ease pain

What are possible complications of septic arthritis in a child?

Septic arthritis can cause joint damage. If your child’s growth plate was affected, this may cause an arm or leg to not grow to the full adult length. The growth plate is the part of the bone where new bone is created. This area of the bone helps determine its final adult length. Make sure to follow up with your child's healthcare provider to prevent long-term problems.

When should I call my child’s healthcare provider?

Tell the healthcare provider if your child’s symptoms get worse or about any new symptoms.

Key points about septic arthritis in a child

• Septic arthritis is an infection in the joint fluid (synovial fluid) and joint tissues. It occurs more often in children than adults.

• Different types of bacteria, viruses, and fungi can infect a joint.

• Symptoms include fever, joint pain, swelling, redness, and warmth.

• Quick treatment with antibiotics if bacteria are the source of infection is needed to stop the risk for joint damage.

• Other treatments include medicines for pain and fever, draining the joint, physical therapy, and splints.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

• Know the reason for the visit and what you want to happen.

• Before your visit, write down questions you want answered.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new directions your provider gives you for your child.

• Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.

• Ask if your child’s condition can be treated in other ways.

• Know why a test or procedure is advised and what the results could mean.

• Know what to expect if your child does not take the medicine or have the test or procedure.

• If your child has a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.