Septic Arthritis – Causes, Treatment and Prevention

Definition

Septic arthritis is also commonly referred to as bacterial or infectious arthritis. It is an intensely painful infection in a joint. Bacteria, viruses, and fungi may invade the joint through various routes that cause inflammation of the synovial membrane. With the onset of inflammation, cytokines and proteases are released, thus resulting in potential joint destruction. The infection is located in the synovial or periarticular tissues and is most commonly bacterial. The image shows Septic arthritis of the left hip joint with melioidosis.

Though uncommon, septic arthritis is an orthopedic emergency that can cause significant joint damage leading to increased morbidity and mortality. Bacteria or other foreign pathogens can infect either one joint or, if left untreated, can spread and cause further systemic damage. Patients and caregivers need to be educated about the severity of this condition and the potential for increased morbidity even after successful antibiotic treatment. It may occur at any age but is more likely in children and older adults. The most commonly targeted joints in the body are the knee, hip, shoulder, ankle, and wrists.

Types of Septic Arthritis

It can occur in various ways, depending on the underlying cause and the specific microorganism involved. The types of septic arthritis can be classified based on different factors. Here are a few common types:

Bacterial Septic ArthritisThis is the most common type, caused by bacteria entering the joint. Bacteria like Staphylococcus aureus can cause this type of infection.

Viral Septic Arthritis: Viruses like hepatitis B, hepatitis C, or parvovirus B19 can infect the joints and cause inflammation.

Fungal Septic Arthritis: Fungal infections in the joints are less common but can happen, especially in people with weakened immune systems or after joint surgery.

Mycobacterial Septic Arthritis: Some specific bacteria, like Mycobacterium tuberculosis, can cause septic arthritis. This type is more common in areas where tuberculosis is widespread.

Reactive Arthritis: This type occurs as a reaction to an infection in another part of the body, like the urinary or digestive system. Certain bacteria, such as Chlamydia or Salmonella, can trigger reactive arthritis.

The type of septic arthritis can vary depending on factors like a person’s health, age, and where they live. It’s important to diagnose the specific type to provide the right treatment for septic arthritis.

Septic Arthritis

Pathophysiology

Septic arthritis involves bacterial infection of a synovial joint. Haematogenous bacterial spread is the most common cause of septic arthritis in children. Osteomyelitis of adjacent bones may also result in joint infection. This is particularly the case in joints where the metaphysis is intracapsular, such as the hip and shoulder. Direct inoculation via penetrating injuries or surgery can occur. The incidence varies between studies, but septic arthritis has a predilection towards children under the age of 4 years. Septic arthritis occurs most commonly in the hip and knee joints. Other joints commonly affected include the shoulder and ankle, but septic arthritis can occur in any synovial joint in the body.

Staphylococcus aureus is the most common pathogen. Other causative organisms include group A Streptococcus and Enterobacter species. Haemophilus influenzae septic arthritis may occur in children who have not been vaccinated. The incidence of Kingella kingae septic arthritis is almost certainly significant but underreported because of its fastidious nature in culture. Proteolytic enzymes released by host inflammatory cells and certain bacteria cause cartilage destruction. Growth plate damage and avascular necrosis of the femoral head are thought to be caused by ischaemia secondary to increased intracapsular pressure.

Epidemiology

The incidence of septic arthritis is between 2 to 6 cases per 100,000 people but varies based on the presence of risk factors. Septic arthritis is more common in children than in adults. The incidence of septic arthritis peaks between ages 2 and 3 years and has a male predominance (2:1). Subgroups of children at high risk include neonates, hemophiliacs with hemarthroses, immunocompromised (e.g., sickle cell anemia, human immunodeficiency virus infection), and those treated with chemotherapy. Risk factors in adults include age older than 80, diabetes mellitus, rheumatoid arthritis, recent joint surgery, joint prosthesis, previous intra-articular injection, skin infections and cutaneous ulcers, Human immunodeficiency virus, osteoarthritis, sexual activity (especially in cases of suspected gonococcal septic arthritis), other causes of sepsis.

Symptoms of Septic Arthritis

In most cases of septic arthritis, the symptoms develop quickly, within a few days. However, with an infection in an artificial joint, the symptoms may not be so dramatic. Pain and fever may be mild at first before gradually becoming worse. Also, in cases caused by the tuberculosis (TB) germ (bacterium), the symptoms may develop more slowly.

• Pain from the affected joint. The pain tends to be severe and develops quite quickly. Any movement of the joint can be very painful.
• Swelling usually develops over the affected joint which is usually very tender.
• Redness of the overlying skin is typical if the joint is near to the skin surface.
• Feeling generally unwell with a high temperature (fever) is common.

Causes of Septic Arthritis

The condition is most commonly caused by either:

• Staphylococcal bacteria
• Streptococcal bacteria

These bacteria may enter a wound and travel through your bloodstream to the affected joint, or may infect your joint directly after an injury or during surgery.

The following things can increase your risk of septic arthritis:

• Having joint surgery, such as a knee replacement or hip replacement
• Having a bacterial infection somewhere else in your body
• Having a long-term condition such as diabetes or rheumatoid arthritis
• Using injected drugs
• Taking medication that suppresses your immune system
• Recently injuring a joint

Risk factors

• Previous joint problems or having chronic diseases that have impacts on the joints. Some of the diseases that may raise the risk of developing septic arthritis are osteoarthritis, gout, rheumatoid arthritis, or lupus. Undergoing joint surgery or having joint injury from the past may also increase the risk.
• Prosthesis joint from joint replacement surgery can cause bacteria to enter the A prosthetic joint can also be infected in the case that infection could spread to the joint by bloodstream.
• Intake of medications for rheumatoid arthritis has an increased risk of developing septic arthritis because the medicines could suppress the immune system, resulting in infection. Patients who have rheumatoid arthritis cannot be easily diagnosed with septic arthritis as the two conditions share common signs and symptoms.
• Fragile skin or skin that can be broken easily and has poor healing properties allows bacteria to enter the body. Psoriasis, eczema and infected wounds on the skin are risk factors of septic arthritis.
• Having weak immune system increases the risk of developing septic arthritis. Patients with diabetes, kidney, and liver diseases fall into this group. As well as those patients who are required to take medicines that suppress immune systems.
• Joint trauma involves direct injury that causes infection to penetrate into the joint directly, such as animal attacks or bites wounds, wounds that are punctured or cuts in the joint.

Patients with a combination of risk factors are at higher risk of developing septic arthritis than those who have a single risk factor.

Complications

It is a serious infection that affects the joints in the body. If not treated quickly, it can cause several complications. Here are some problems that can arise from septic arthritis:

1. Joint Damage: The infection can harm the cartilage in the joint, making it difficult to move the affected joint and causing long-term disability.
2. Bone Infection: Sometimes, the infection can spread from the joint to the nearby bone, leading to a bone infection called osteomyelitis. This can cause further damage to the bone and slow down the healing process.
3. Blood Poisoning: The infection can enter the bloodstream and cause blood poisoning, known as septicemia. This can result in severe problems throughout the body, such as organ failure and even death if not treated promptly.
4. Pus Buildup: Pockets of pus, called abscesses, can form within the joint or nearby tissues. These abscesses can damage the joint and make it harder for it to heal properly.
5. Chronic or Recurring Infections: In some cases, septic arthritis may persist or come back even after treatment. This can lead to ongoing joint inflammation, pain, and repeated infections.
6. Limited Joint Movement: Due to pain, inflammation, and damage to the joint, people with septic arthritis may find it difficult to move the affected joint. This can greatly affect their ability to move around and enjoy daily activities.
7. Other Complications: Depending on the location and severity of the infection, septic arthritis can cause additional problems such as unstable joints, weak muscles, deformities, and infections in nearby tissues.

If you suspect septic arthritis, it’s important to see a doctor right away to reduce the risk of these complications. Early diagnosis, proper antibiotics, drainage of infected fluid from the joint, and supportive care are essential in managing septic arthritis and preventing long-term problems.

How to diagnosis septic arthritis?

Prompt diagnosis of septic arthritis is necessary to prevent permanent damage to the joint.

In addition to a complete medical history and physical examination, clinical experts at The Children’s Hospital of Philadelphia use a variety of methods to diagnose septic arthritis:

• Removing and culturing joint fluid to determine the type of bacteria causing the infection, how well your child’s body is fighting the infection, and the appropriate antibiotic to treat the infection.
• Bacterial cultures can be obtained if there is concern an infection in another part of the body has spread to the joint.
• Blood tests can determine if there is evidence of systemic inflammation.
• X-rays visualize bones and surrounding tissues of an affected joint.
• Ultrasounds can visualize extra fluid in a joint and can help guide a needle into a joint to obtain joint fluid.
• Bone scans may be used to identify other sites of infection if the joint is not suspected to be the primary site of infection
• Magnetic resonance imaging (MRI) produces detailed images of organs and structures within the body.

Treatment

Doctors rely on joint drainage and antibiotic drugs to treat septic arthritis.

Joint drainage

Removing the infected joint fluid is crucial. Drainage methods include:

• Needle. In some cases, your doctor can withdraw the infected fluid with a needle inserted into the joint space.
• Scope procedure. In arthroscopy (ahr-THROS-kuh-pee), a flexible tube with a video camera at its tip is placed in your joint through a small incision. Suction and drainage tubes are then inserted through small incisions around your joint.
• Open surgery. Some joints, such as the hip, are more difficult to drain with a needle or arthroscopy, so an open surgical procedure might be necessary.

Antibiotics

To select the most effective medication, your doctor must identify the microbe causing your infection. Antibiotics are usually given through a vein in your arm at first. Later, you may be able to switch to oral antibiotics.

Typically, treatment lasts from two to six weeks. Antibiotics carry a risk of side effects, including nausea, vomiting and diarrhea. Allergic reactions also can occur. Ask your doctor about what side effects to expect from your medication.

Removal of replacement joint

If an artificial joint is infected, treatment often involves removing the joint and temporarily replacing it with a joint spacer a device made with antibiotic cement. Several months later, a new replacement joint is implanted.

If a replacement joint can’t be removed, a doctor may clean the joint and remove damaged tissue but keep the artificial joint in place. Intravenous antibiotics are followed by oral antibiotics for several months to prevent the infection from coming back.

Prevention of septic arthritis

While not all cases of septic arthritis are preventable, there are a few things you can do to try to prevent getting it, including:

• Make sure cuts and wounds don’t get infected: If you have a cut or wound on your skin, keep it clean to prevent infection. If you are experiencing signs of an infection — such as redness, warmth and/or pus in or around your wound contact your healthcare provider immediately.
• Try to manage your chronic health condition(s) well: If you have a chronic health condition such as diabetes or AIDS (acquired immunodeficiency syndrome), try to manage your condition as well as you can in order to stay healthy.
• Practice safe sex: Always follow safe sex practices, such as always using a condom or dental dam and talking with your sexual partner about past partners and STI (sexually transmitted infection) history.
• Don’t abuse drugs: Injection drug use can cause infections. Only take medications as prescribed by your healthcare provider.