What to Know about
Septic Arthritis

What is septic arthritis?

Septic arthritis is a serious and painful type of arthritis that occurs when a joint becomes infected. As such, it should be treated as soon as possible after symptoms appear, or diagnosis is made, as the infection can rapidly spread and cause severe damage to the joint.

Septic arthritis can occur when pathogens (germs) gain access to a joint, most commonly through bloodstream circulation of pathogen causing a urinary tract infection or skin infection; otherwise, it can be caused by a penetrating wound or injury or as a complication of surgery.

Treatment of septic arthritis involves draining the infected joint surgically, or with a fine needle, and treating the infection with an appropriate antibiotic.

How do you know you have septic arthritis?

Symptoms of septic arthritis include:

• Very severe pain, usually in one joint, that comes on suddenly. The knees are most commonly affected, but septic arthritis also affects the other large joints, namely the hips and shoulders, as well as other smaller other joints.
• The affected joint is usually swollen, red and warm to the touch.
• If you have septic arthritis, you might feel unwell and will probably have a fever.

When to see your doctor:
See your doctor immediately if you have severe pain in a joint that starts suddenly.

What causes septic arthritis?

Bacterial, viral and fungal pathogens can all cause septic arthritis; however, the most common cause is with the bacteria Staphylococcus aureus (commonly known as a ‘staph infection’).

• Septic arthritis can develop when pathogens from a skin infection (Staph live on normal, healthy skin) or urinary tract infection spread in your bloodstream to a joint.
• Less commonly, puncture wounds (such as from a cut or animal bite), drug injections, or recent surgery in, or near, a joint can give the germs entry into the joint space.

You are more likely to get septic arthritis based on the following combination of risk factors:

• Existing joint problems: Having chronic joint disease, like other types of arthritis, increases your risk of developing septic arthritis.
• Artificial joints, previous joint surgery or past joint injury: If you have had surgical procedures on joints, like hip or knee arthroplasty (replacement), and recent or past joint injuries, you are at increased risk of developing septic arthritis.
• Conditions that weaken the immune system: This can include chronic conditions like diabetes and kidney disease, as well as immunosuppressive medications like those used for rheumatoid arthritis.
• Skin fragility: Skin conditions such as psoriasis and eczema, which dry and weaken the skin, causing it to break easily, increase your risk of septic arthritis, as bacteria like Staph aureus can more easily gain entry to the body.
  Infected wounds and using intravenous (injectable) drugs like heroin also increase this risk.

How is septic arthritis diagnosed?

Your doctor will probably use the following tests to diagnose you with septic arthritis:

• Joint fluid analysis: Here, a fine needle will be inserted into the joint space to withdraw synovial fluid (fluid inside the joint). Laboratory tests can determine if the joint is infected and, if so, by which pathogen(s), so that the correct medication can be used in your treatment.
• Blood tests: Your doctor will probably ask to collect blood from you to test for signs of infection.
• Radiography: X-ray can also be used to assess the damage to your joint.

How is septic arthritis treated?

If you are diagnosed with septic arthritis, your doctor will use the following in your treatment:

• Joint drainage: This involves removing infected fluid from the joint by either fine needle aspiration, arthroscopy (a scope procedure using a camera at the end of a flexible tube to guide a needle into the joint for suction) or open surgery.
• Antibiotic treatment: Your doctor will use a type of medication that specifically kills the pathogen causing your rheumatoid arthritis.
  Your doctor or healthcare provider will probably start your antibiotic treatment intravenously or through a drip in your arm when you are first diagnosed. However, treatment can last anywhere from two to six weeks, and you must complete the entire course of antibiotics, and cannot stop taking your medication before the course is finished, as this can lead to treatment failure and the infection coming back, and can also contribute to antibiotic resistance.

It is important that you seek medical attention immediately if you think you have septic arthritis, as the immune response in joints is reduced by the limited blood flow to these areas and a limited acute inflammatory response inside the joints cannot properly eliminate pathogens. Therefore, your body cannot fight the infection without help.

What are the complications of septic arthritis?

If septic arthritis goes untreated, or treatment is delayed, it can lead to joint degeneration and permanent joint damage, or even widespread, systemic sepsis which can be life-threatening.