Septic arthritis
Septic arthritis is the purulent invasion of a joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...

 by an infectious
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

 agent which produces arthritis
Arthritis is a form of joint disorder that involves inflammation of one or more joints....

. People with artificial joints
Joint replacement
Replacement arthroplasty [from Greek arthron, joint, limb, articulate, + -plassein, to form, mould, forge, feign, make an image of], or joint replacement surgery, is a procedure of orthopedic surgery in which the arthritic or dysfunctional joint surface is replaced with an orthopaedic prosthesis...

 are more at risk than the general population but have slightly different symptoms, are infected with different organisms and require different treatment. Septic arthritis is considered a medical emergency. If untreated, it may destroy the joint in a period of days. The infection may also spread to other parts of the body.


The term "suppurative arthritis" is a near synonym for septic arthritis. ("Suppurative" refers to the production of pus
Pus is a viscous exudate, typically whitish-yellow, yellow, or yellow-brown, formed at the site of inflammatory during infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection of pus within or beneath the epidermis is known as a pustule or...

, without necessarily implying sepsis
Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...


The International Statistical Classification of Diseases and Related Health Problems, 10th Revision is a medical classification list for the coding of diseases, signs and symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or diseases, as maintained by the...

 uses the term "pyogenic arthritis". Pyogenic also refers to the production of pus.

Reactive arthritis
Reactive arthritis
Reactive arthritis , is classified as an autoimmune condition that develops in response to an infection in another part of the body. Coming into contact with bacteria and developing an infection can trigger the disease. Reiter's syndrome has symptoms similar to various other conditions collectively...

 refers to arthritis caused by an immune consequence of an infection, but not directly attributable to the infection itself.

The usual etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....

 of septic arthritis is bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l, but viral
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

, mycobacterial, and fungal
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 arthritis occur occasionally. A broader term is "infectious arthritis", which describes arthritis caused by any infectious organism. Viruses can cause arthritis, but it can be hard to determine if the arthritis is directly due to the virus or if the arthritis is reactive.

Septic/suppurative arthritis and "bacterial arthritis" are sometimes considered equivalent, but there are exceptions. For example, Borrelia burgdorferi
Borrelia burgdorferi
Borrelia burgdorferi is a species of Gram negative bacteria of the spirochete class of the genus Borrelia. B. burgdorferi is predominant in North America, but also exists in Europe, and is the agent of Lyme disease....

can cause infectious arthritis, but is not associated with suppurative arthritis.


Bacteria are carried by the bloodstream from an infectious focus elsewhere, introduced by a skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...

 that penetrates the joint, or by extension from adjacent tissue (e.g. bone or bursae bovine tb).

Micro-organisms must reach the synovial membrane of a joint. This can happen in any of the following ways:
  • dissemination of pathogen
    A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

    s via the blood, from abscess
    An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

    es or wound infections, or from an unknown focus
  • dissemination from an acute osteomyelitic focus
    Osteomyelitis simply means an infection of the bone or bone marrow...

  • dissemination from adjacent soft tissue
    Soft tissue
    In anatomy, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body, not being bone. Soft tissue includes tendons, ligaments, fascia, skin, fibrous tissues, fat, and synovial membranes , and muscles, nerves and blood vessels .It is sometimes...

  • entry via penetrating trauma
    Penetrating trauma
    Penetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out...

  • entry via iatrogenic means.

Bacteria that are commonly found to cause septic arthritis are:
  • Staphylococcus aureus
    Staphylococcus aureus
    Staphylococcus aureus is a facultative anaerobic Gram-positive coccal bacterium. It is frequently found as part of the normal skin flora on the skin and nasal passages. It is estimated that 20% of the human population are long-term carriers of S. aureus. S. aureus is the most common species of...

     - the most common cause in adults
  • Streptococci
    Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

     - the second most common cause
  • Haemophilus influenzae
    Haemophilus influenzae
    Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, Gram-negative, rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H...

     - was the most common cause in children but is now uncommon in areas where Haemophilus vaccination is practiced
  • Neisseria gonorrhoea
    Gonorrhea is a common sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. The usual symptoms in men are burning with urination and penile discharge. Women, on the other hand, are asymptomatic half the time or have vaginal discharge and pelvic pain...

     - in young adults (now thought rare in Western Europe
    Western Europe
    Western Europe is a loose term for the collection of countries in the western most region of the European continents, though this definition is context-dependent and carries cultural and political connotations. One definition describes Western Europe as a geographic entity—the region lying in the...

  • Escherichia coli
    Escherichia coli
    Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

     - in the elderly, IV drug users and the seriously ill
  • M. tuberculosis, Salmonella
    Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...

     spp. and Brucella
    Brucella is a genus of Gram-negative bacteria. They are small , non-motile, non-encapsulated coccobacilli, which function as facultative intracellular parasites....

     spp. - cause septic spinal arthritis

In bacterial infection, Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

 has been found to infect joints, especially in children who have sustained a puncture wound. This bacteria also causes endocarditis
Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or even on intracardiac devices...



Septic arthritis should be considered whenever one is assessing a patient with rapid onset of joint pain. Usually only one joint is affected (monoarthritis
Monoarthritis is inflammation of one joint at a time. It is usually caused by trauma, infection, or crystalline arthritis.-Diagnosis:...

) however in seeding arthritis, several joints can be affected simultaneously; this is especially the case when the infection is caused by staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....

 or gonococcus bacteria. Pain can be significant with any movement, therefore, patient will refuse to use extremity and prefers to hold joint rigidly. May have associated swelling, redness & warmth, often absent for deep joints such as hips & shoulders.

The diagnosis of septic arthritic can be difficult as no test is able to completely rule out the possibility.

A number of factors should increase one's suspicion of the presence of an infection. In children these are: fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

 > 38.5 C, non-weight-bearing, serum WBCs > 12 x 10^9, ESR
Erythrocyte sedimentation rate
The erythrocyte sedimentation rate , also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour...

 > 40 mm/hr, CRP
-Biochemistry and medicine:* C-reactive protein , an acute phase protein produced by the liver* cAMP receptor protein is a regulatory protein in bacteria* Collagen-related peptides...

 > 20 mg/dL, a previous visit for the same.

Diagnosis is by aspiration (giving a turbid, non-viscous fluid), Gram stain and culture
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...

 of fluid from the joint, as well as tell-tale signs in laboratory testing (such as a highly elevated neutrophils (approx. 90%), ESR
Erythrocyte sedimentation rate
The erythrocyte sedimentation rate , also called a sedimentation rate or Biernacki Reaction, is the rate at which red blood cells sediment in a period of 1 hour...

 or CRP
-Biochemistry and medicine:* C-reactive protein , an acute phase protein produced by the liver* cAMP receptor protein is a regulatory protein in bacteria* Collagen-related peptides...

). The ESR and CRP are almost always raised on admission, CRP being faster in diagnostics.

The Gram stain can rule in the diagnosis of septic arthritis however cannot exclude it.

X-rays - may not be helpful early, but may show subtle increase in joint space tissue swelling.

Ultrasound - may reveals joint effusion.


Therapy is usually with intravenous antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

s, analgesia and washout/aspiration of the joint to dryness. Among pediatric patients with an acute hematogenous septic arthritis a short total course of 10 days of antimicrobials is sufficient in uncomplicated cases.

In infection of a prosthetic joint, a biofilm is often created on the surface of the prosthesis which is resistant to antibiotics. Surgical debridement or arthrotomy is usually indicated in these cases.
A replacement prosthesis is usually not inserted at the time of removal to allow antibiotics to clear infection of the region.

Patients in whom surgery is contraindicated may trial long-term antibiotic therapy.

Close follow up with physical exam & labs must be done to make sure patient remain afebrile, pain resolved, improved range of motion and normalized lab values.

Radiologic findings

The diagnosis of septic arthritis is based on clinical assessment and prompt arthrocentesis
Arthrocentesis is the clinical procedure of using a syringe to collect synovial fluid from a joint capsule. It is also known as joint aspiration. Arthrocentesis is used in the diagnosis of gout, arthritis, and synovial infections....

. Imaging can sometimes be used to aid in the diagnosis of septic arthritis.

Native X-ray of the joint is neither sensitive nor specific. Ultrasound can detect joint-swelling. MRI findings include: synovial enhancement, perisynovial edema and joint effusion. Signal abnormalities in the bone marrow can indicate a concomitant osteomyelitis. The sensitivity and specificity of MRI for the detection of septic arthritis has been reported to be 67% and 98% respectively.

See also

  • Arthritis
    Arthritis is a form of joint disorder that involves inflammation of one or more joints....

  • Human biting injuries
  • Transient synovitis
  • Arthritis Care
    Arthritis Care
    Arthritis Care is the UK's largest charity dedicated to supporting people with arthritis . It is a user led organisation which means people with arthritis are at the heart of its work – they form its membership, are involved in its activities and are well represented on its staff and board of...

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