What is Septic Arthritis, Know its Causes, Symptoms, Treatment, Risk Factors, Complications, Diagnosis

Septic arthritis is a condition characterised by infection in the joints. The word ‘septic’ refers to infection caused by invasion and multiplication of pathogenic micro-organisms which are usually not present within the human body. These include invasion by bacteria, viruses, and other parasites. Septic conditions or infections may be subclinical without apparent symptoms, or it may produce clinical symptoms. Infections may either be localized to a particular area or it may spread to other areas through the blood vessels or lymphatic channel.

Arthritis is an orthopaedic condition characterised by inflammation of the joints. It may affect a single joint or may affect multiple joints. Arthritis can be of many kinds based on the causes and symptoms of the condition; the most types being osteoarthritis and rheumatoid arthritis. It usually affects adults above the age of 65 years and rarely affects the younger population. The symptoms develop gradually and worsen over a period of time in most the cases.

What is a Septic Arthritis?

What is a Septic Arthritis?

Inflammation of joint when accompanied by infection is called as septic arthritis. It is also known as infectious arthritis and it is most commonly caused by bacteria due to their rapid destructive nature. Septic arthritis can also be caused by other pathogens such as fungi, viruses and mycobacteria. In most of the cases, septic arthritis affects one large joint such as the hip joint or the knee joint. In a few cases, it has been seen that multiple joints have been affected by septic arthritis. The incidence of septic arthritis has been increasing lately with increased use of prosthetic joints.

Based on the cause of infection, septic arthritis can be classified as:

  • Gonococcal or non-gonococcal septic arthritis
  • Prosthetic joint infection
    • Early cases, which occurs within 3 months of implantation
    • Delayed cases, which occurs within 3-24 months of implantation
    • Late cases, which occurs 24 months after implantation.

Symptoms of Septic Arthritis

The onset of septic arthritis is often sudden in nature associated with severe pain, swelling in the joints and fever. Other commonly encountered symptoms of Septic arthritis include:

  • Chills
  • Fatigue and weakness
  • Fever
  • Difficulty with movement
  • Pain and tenderness over the affected joint that worsens with movement
  • Increased fluid accumulation over the affected joint with swelling
  • Warmth and redness over the area, predominantly due to increased blood flow over the area can also be a symptom of Septic arthritis.

Epidemiology of Septic Arthritis

Studies have shown that the incidence of septic arthritis in United States is about 7.8 cases in 100,000 people per year. About 20,000 cases of septic arthritis are reported in the United Sates every year. Gonococcal infection has an incidence rate of about 2.8 cases per 100,000 people per year. The incidence of septic infection in prosthesis recipients is about 2 to 10%. It can also occur in individuals with compromised immune system and aged population. Septic arthritis is more common among individuals who are above the age of 65 years. It has been noticed that about 56% of total septic arthritis cases are seen in males.

Causes of Septic Arthritis

Septic arthritis is usually caused by bacterial infection that spreads from one area to another area through the blood stream. It is often caused due to bacterial invasion in an open wound or a post-surgical wound, such as knee surgery, which leads to infection over the joint causing pain and inflammation. The most common bacteria that cause acute septic arthritis are:

  • Haemophilus influenza
  • Staphylococcus
  • Streptococcus

Septic arthritis may also be caused by other agents such as viruses and fungi. Causative viruses include:

Fungi that have the ability to cause septic arthritis include:

  • Coccidiomyces
  • Histoplasma
  • Blastomyces.

Risk Factors of Septic Arthritis

Young children and adults above the age of 65 years are at maximum risk of developing septic arthritis, predominantly in patients with open wound or history of prosthetic implants. Other risk factors of septic arthritis includes

  • Weakened immune system
  • Diabetes
  • Cancer
  • History of intra venous drug abuse
  • Auto immune disorders
  • History of previously damaged joints.

People with any of the above mentioned conditions possess a threat for development of septic arthritis.

Complications of Septic Arthritis

Septic arthritis often leads to difficulty with movement. About 50 percent of the Septic arthritis patients develop recurrent episodes of decreased range of motion and chronic pain post infection. Over a period of time, if left untreated, septic arthritis can lead to osteomyelitis, sepsis and dysfunctional joints. Predictors of poor outcome include:

  • Age above 60 years
  • Infection in hip and shoulder joints
  • Presence of underlying condition such as rheumatoid arthritis
  • Positive findings on culture after 7 days post treatment
  • A delay of more than 7 days in providing appropriate treatment.

Diagnosis of Septic Arthritis

Diagnosis of septic arthritis is usually done by an experienced orthopaedist. In most of the cases, intervention by a rheumatologist is needed. A detailed case history is obtained followed by physical examination of the affected joint. Diagnostic procedure includes arthrocentesis, which involves surgical puncture of the affected joint to collect the synovial fluid. A needle is inserted into the joint, and the synovial fluid is drawn from the joint. This fluid is then sent to the lab for investigation and culture. In positive cases, the white blood cell count is generally above normal limits. A culture is done to determine the causative pathogen. A blood work may be done to look for and signs of inflammation. X-rays are done to examine bone damages. MRI is usually helpful in advanced cases.

Treatment of Septic Arthritis

Treatment of Septic arthritis involves the following:

  • Administration of antibiotics based on the cause of septic arthritis. Antibiotics help in arresting spread of the infection.
  • Antibiotics to treat Septic arthritis may be given intravenously or orally specific to the causative organism.
  • Drainage of infected synovial fluid is often beneficial in treating Septic arthritis. It is done with the help of a needle and a syringe.
  • Arthroscopy is done to irrigate and remove infected tissue.
  • In severe cases, open joint surgery may be considered to drain the infectious material.
  • In case of excessive fluid built up, the drains are left in place for fluid removal post-surgery.


Septic arthritis is medical condition where there is infection in the joints. Septic arthritis generally affects one large joint such as the knee, hip or the shoulder and very rarely affects multiple joints at once. Septic arthritis is generally caused by spread of infection from other parts of the body, such as an open wound, post-surgical site, prosthetic implants etc. Septic arthritis is left untreated, can lead to severe complications and can lead to permanent disability. It is an infectious disease and should be treated at the earliest.

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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 22, 2022

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