Definition

Septic arthritis is an infection of a joint that has spread through the bloodstream, causing joint pain and other symptoms of infection. Also known as pyogenic or suppurative arthritis, this condition is most commonly caused by bacterial microorganisms. However, it can also result from puncture wounds, such as animal bites, or other injuries that allow bacteria or viruses to enter the joint.

This disease typically affects large joints, such as the knee or hip. The infection causes inflammation in the joint lining, leading to swelling and reduced blood flow to the affected area. This can ultimately damage the tissues surrounding the joint.

Read more about Arthritis on the following Ai Care page: Arthritis—Definition, Cause, Symptom, and Management

Causes

Septic arthritis can be caused by microorganisms, including bacteria, viruses, or fungi. The most common bacterial cause is Staphylococcus aureus. The synovial membrane (joint lining) has limited ability to protect the joint from infections, so when an infection occurs, the blood flow to the joint decreases, leading to joint damage.

Septic arthritis can develop when an infection from another part of the body, such as the skin or urinary tract, spreads through the bloodstream to the joints.

Other, less common causes include:

• Puncture wounds
• Drug injections
• Surgery near the joint area, including joint replacement surgery

Risk Factor

Septic arthritis is more common in infants and older adults. However, several factors can increase the risk of developing septic arthritis, including:

• History of joint problems. Chronic joint conditions such as osteoarthritis, gout, rheumatoid arthritis, or lupus can increase the risk.
• Joint surgery history. Previous surgeries, including the placement of artificial joints, can introduce bacteria to the joint area.
• Joint trauma. Injuries such as animal bites, puncture wounds, or torn joints can increase the risk of septic arthritis.
• Compromised immune system. Diseases that weaken the immune system, such as diabetes, kidney or liver disease, and the use of immunosuppressive drugs, can raise the risk.
• Skin vulnerability. Conditions that make the skin prone to damage, such as psoriasis or eczema, make it harder to treat and more susceptible to infection.

Symptoms

The primary symptoms of septic arthritis include severe pain and discomfort in the affected joint, accompanied by swelling, redness, and warmth. Some people may also experience fever. Infants with septic arthritis may become irritable and cry when the affected joint is moved, such as during diaper changes.

Septic arthritis involving an artificial joint may present with mild pain and swelling that develops over several months or years after the joint surgery. Joint dislocation can also occur, causing pain during movement, which may subside at rest.

Diagnosis

Doctors may use several methods to diagnose septic arthritis, including:

• Joint fluid analysis (arthrocentesis). Infection can be identified by the color, consistency, and volume of the joint fluid.
• Blood tests. These help determine if the infection has spread into the bloodstream and monitor signs of infection. Blood samples are typically taken from a vein.
• X-rays or other imaging tests. These are used to assess the extent of damage caused by the infection.

Management

Treatment for septic arthritis depends on the cause and severity of the condition, as determined by a doctor. Generally, septic arthritis can be treated with antibiotics and joint drainage.

Antibiotics

The doctor will identify the cause of the joint infection and administer the appropriate type of antibiotics intravenously. After the initial phase, oral antibiotics may be prescribed.

The choice of antibiotic depends on the type of bacteria involved. Antibiotic treatment typically lasts for about 2-6 weeks.

Joint Drainage

Joint drainage is a crucial procedure in managing septic arthritis. There are several methods a doctor might use to remove infected joint fluid:

• In some cases, fluid can be withdrawn using a needle inserted into the joint.
• An arthroscopy may be performed, where a small incision is made in the joint to insert a camera and suction out the fluid.
• Open surgery may be necessary for joints that are difficult to drain using the above methods, such as the hip joint.

For individuals with infections caused by artificial joints, the prosthetic joint may need to be removed. The infected joint is taken out, and a new one is implanted after several months. Patients will also receive intravenous and oral antibiotics to prevent recurrence of the infection.

Complications

If a joint becomes infected and septic arthritis develops, inflammation and reduced blood circulation can lead to joint damage. Potential complications include:

1. Joint degeneration
2. Permanent joint damage
3. Joint dislocation

When to See a Doctor?

Septic arthritis is a serious condition that requires prompt medical attention. See a doctor if you experience sudden, severe joint pain. You may want to consult a rheumatologist or orthopedic specialist. If you have a history of joint replacement surgery, seek medical attention immediately if you experience pain while using the joint.

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