Definition

Septic arthritis is a serious infection of the joints caused by bacteria. This infection causes the joint to be filled with pus cells. These pus cells release substances directed against the bacteria. However, this action can damage the joint structures, bone, and surrounding cartilage.

This condition should be treated as a medical emergency. If left untreated, it causes loss of function in the affected joint. It can lead to septic shock, a potentially fatal condition. With early treatment, recovery is usually good.

Causes

Septic arthritis develops when bacteria spreads from the source of infection through the bloodstream to a joint. It can result from:

• Infection due to an injection
• Surgery
• Other infections

Septic arthritis can also be caused from injury or trauma. It can result from:

• A penetration wound
• An injury that affects the joint

Septic arthritis can strike at any age. But, it occurs most often in children aged three and younger. In infants, the hip is a frequent site of infection. In toddlers, it is the shoulders, knees, and hips. In children, the most common bacterial causes are:

• Staphylococcus aureus ( staph infection)
• Streptococcus species (eg, group B strep infection)
• Streptococcus pneumoniae (a common bacterial cause of pneumonia)

Septic arthritis rarely occurs from early childhood through adolescence. After that, its occurs more often. In adults, it most commonly affects weight-bearing joints, such as the knees. In adults, the most common causes are:

• Staphylococcus aureus
• Neisseria gonorrhoeae (the bacteria that causes gonorrhea)

Joint Damage in Knee

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Risk Factors

The following factors increase your chance of developing septic arthritis. If you have any of these risk factors, tell your doctor:

• Diseases that weaken the immune system, such as HIV, or taking drugs that suppress immunity
• A history of joint problems or having other types of arthritis, gout, or lupus
• A history of IV drug use
• Chronic illnesses (eg, anemia, diabetes, sickle cell, kidney failure)
• Joint replacement or organ transplant surgery
• Recent injections (eg, cortisone or hyaluronic acid)
• Skin conditions (eg, psoriasis, eczema)

Symptoms

If you experience any of these symptoms do not assume it is because of septic arthritis. These symptoms may be caused by other, less serious conditions.

• Newborn or infants
  • Crying when a joint is moved (eg, during a diaper change)
  • Immobility of the limb of a joint
  • Swelling and redness
  • Irritability
  • Fever
  • Persistent crying for any reason
• Children and adults
  • Intense joint pain
  • Joint swelling and redness
  • Fever
  • Chills
  • Immobility of a joint or its limb

Diagnosis

Your doctor will ask about you or your child’s symptoms and medical history. A physical exam will be done. Your doctor may refer you to a specialist.

Your doctor may need to test your bodily fluids. This can be done with:

• Synovial fluid (fluid that lubricates the joint) testing
• Blood tests

Your doctor may need pictures of your joints. This can be done with x-rays.

Treatment

Antibiotic therapy is started as soon as a diagnosis is made. In the beginning, antibiotics are given by IV. This is to ensure that the infected joint receives medicine to kill the bacteria. The specific medicines used depend on the type of bacteria that is causing the infection. The remaining course of antibiotics may be given orally.

Fluid may be removed from the joint to reduce the likelihood of joint damage. This may be done either by placing a needle in the joint or through surgery.

Rest, preventing the joint from moving, and warm compresses may be used to manage pain. Physical therapy or exercises may also speed recovery.

If you are diagnosed with septic arthritis, follow your doctor's instructions.

Prevention

To help reduce your chance of getting septic arthritis, get prompt treatment of infections that could lead to septic arthritis.