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Acute septic arthritis, infectious arthritis, suppurative arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typically include redness, heat and pain in a single joint associated with a decreased ability to move the joint. Onset is usually rapid. Other symptoms may include
fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, weakness and headache. Occasionally, more than one joint may be involved, especially in neonates and younger children. In neonates, infants during the first year of life, and toddlers, the signs and symptoms of septic arthritis can be deceptive and mimic other infectious and non-infectious disorders. In children, septic arthritis is usually caused by non-specific bacterial infection and commonly
hematogenous Bloodstream infections (BSIs), which include bacteremias when the infections are bacterial and fungemias when the infections are fungal, are infections present in the blood. Blood is normally a sterile environment, so the detection of microb ...
, i.e., spread through the bloodstream. Septic arthritis and/or acute hematogenous osteomyelitis usually occurs in children with no co-occurring health problems. Other routes of infection include direct trauma and spread from a nearby abscess. Other less common cause include specific
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
as mycobacterium tuberculosis, viruses,
fungi A fungus ( : fungi or funguses) is any member of the 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, separately fr ...
and parasites. In children, however, there are certain groups that are specifically vulnerable to such infections namely preterm infants, neonates in general, children and adolescence with hematologic disorders, renal osteodystrophy and immune-compromised status. In adults vulnerable groups include an artificial joint, prior arthritis,
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
and poor immune function. Diagnosis is generally based on accurate correlation between history-taking and clinical examination findings and basic laboratory and imaging findings like joint ultrasound. In children septic arthritis can have serious consequences if not treated appropriately and timely. Initial treatment typically includes
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and preventio ...
such as
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
,
ceftriaxone Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and join ...
or ceftazidime. Surgery in the form of joint drainage is the gold standard management in large joints like the hip and shoulder. Without early treatment, long-term joint problems may occur, such as irreversible joint destruction and dislocation.


Signs and symptoms


Children

In children septic arthritis usually affects the larger joints like the hips, knees and shoulders. The early signs and symptoms of septic arthritis in children and adolescence can be confused with limb injury. Among the signs and symptoms of septic arthritis are: acutely swollen, red, painful joint with fever. Kocher criteria have been suggested to predict the diagnosis of septic arthritis in children. Importantly, observation of active limb motion or kicking in the lower limb can provide valuable clues to septic arthritis of hip or knee. In neonates/new born and infants the hip joint is characteristically held in abduction flexion and external rotation. This position helps the infant accommodate maximum amount of septic joint fluid with the least tension possible. The tendency to have multiple joint involvements in septic arthritis of neonates and young children should be closely considered.


Adults

In adults, septic arthritis most commonly causes pain, swelling and warmth at the affected joint. Therefore, those affected by septic arthritis will often refuse to use the extremity and prefer to hold the joint rigidly.
Fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
is also a symptom; however, it is less likely in older people. In adults the most common joint affected is the knee. Hip, shoulder, wrist and elbow joints are less commonly affected. Spine, sternoclavicular and sacroiliac joints can also be involved. The most common cause of arthritis in these joints is recurrent infections such as STD’s or URI’s with bacteria, mycobacteria, fungi, etc. > Usually, only one joint is affected. More than one joint can be involved if bacteria are spread through the bloodstream.


Prosthetic joint

For those with artificial joint implants, there is a chance of 0.86 to 1.1% of getting infected in a knee joint and 0.3 to 1.7% of getting infected in a hip joint. There are three phases of artificial joint infection: early, delayed and late. * Early – infection occurs in less than 3 months. Usual signs and symptoms are fever and joint pain, with redness and warmth over the joint operation site. The mode of infection is during the joint implant surgery. The usual bacteria involved are '' Staphylococcus aureus'' and gram negative bacilli. * Delayed – infection occurs between 3 and 24 months. There would be persistent joint pain, due to loosening of the implant. The mode of infection is during the implant surgery. Common bacteria are coagulase-negative '' Staphylococcus'' and '' Cutibacterium acnes''. * Late – more than 24 months. It is usually presented with a sudden onset of joint pain and fever. The mode of infection is through the bloodstream. The bacteria involved are the same as those in septic arthritis of a normal joint.


Cause

Septic arthritis is most commonly caused by a bacterial infection. Bacteria can enter the joint by: * The bloodstream from an infection elsewhere (most common) * Direct penetration into the joint (
arthrocentesis Arthrocentesis, or joint aspiration, is the clinical procedure performed to diagnose and, in some cases, treat musculoskeletal conditions. The procedure entails using a syringe to collect synovial fluid from or inject medication into the joint caps ...
, arthroscopy, trauma) * A surrounding infection in the
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
or tissue (uncommon, from osteomyelitis, septic bursitis,
abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends ...
). Microorganisms in the blood may come from infections elsewhere in the body such as wound infections, urinary tract infections, meningitis or
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 the ...
. Sometimes, the infection comes from an unknown location. Joints with preexisting arthritis, such as
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...
, are especially prone to bacterial arthritis spread through the blood. In addition, some treatments for rheumatoid arthritis can also increase a person's risk by causing an immunocompromised state. Intravenous drug use can cause
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 the ...
that spreads bacteria in the bloodstream and subsequently causes septic arthritis. Bacteria can enter the joint directly from prior surgery,
intraarticular injection In medicine, a joint injection (intra-articular injection) is a procedure used in the treatment of inflammatory joint conditions, such as rheumatoid arthritis, psoriatic arthritis, gout, tendinitis, bursitis, Carpal Tunnel Syndrome, and occasion ...
,
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...
or joint prosthesis.


Risk factors

In children, although septic arthritis occurs in healthy children and adolescents with no co-occurring health issues, there are certain risk factors that may increase the likelihood of acquiring septic arthritis. For example, children with renal osteodystrophy or renal bone disease, certain hematological disorders and diseases causing immune suppression are risk factors for childhood septic arthritis. The rate of septic arthritis varies from 4 to 29 cases per 100,000 person-years, depending on the underlying medical condition and the joint characteristics. For those with a septic joint, 85% of the cases have an underlying medical condition while 59% of them had a previous joint disorder. Having more than one risk factor greatly increases risk of septic arthritis. * Age over 80 years *
Diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
*
Osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the ...
*
Rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...
. Risk of septic arthritis increases with anti-
tumor necrosis factor alpha Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolo ...
treatment. * Immunosuppressive medication *
Intravenous drug abuse Drug injection is a method of introducing a drug into the bloodstream via a hollow hypodermic needle, which is pierced through the skin into the body (usually intravenously, but also at an intramuscular or subcutaneous location). Intravenous t ...
* Recent joint surgery * Hip or knee prosthesis and skin infection * HIV infection * Other causes of
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...


Organisms

Most cases of septic arthritis involve only one organism; however, polymicrobial infections can occur, especially after large open injuries to the joint. Septic arthritis is usually caused by
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
, but may be caused by viral, mycobacterial, and fungal pathogens as well. It can be broadly classified into three groups: non-gonococcal arthritis, gonococcal arthritis, and others. * Non-gonococcal arthritis – These
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
account for over 80% of septic arthritis cases and are usually staphylococci or
streptococci ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occu ...
. Such infections most commonly come from drug abuse, cellulitis,
abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends ...
es, endocarditis, and chronic osteomyelitis. Methicillin-resistant ''Staphylococcus aureus'' (MRSA) may affect 5 to 25% of the cases while gram negative bacilli affects 14 to 19% of the septic arthritis cases. Gram negative infections are usually acquired through urinary tract infections, drug abuse, and skin infections. Older people who are immunocompromised are also prone to get gram negative infections. Common gram negative organisms are: ''
Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. a ...
'' and ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
''. Both gram positive and gram negative infections are commonly spread through the blood from an infective source; but can be introduced directly into the joint or from surrounding tissue. It often affects older people, and often happens suddenly, involving only one joint. Joint aspiration cultures are positive in 90% of cases, while only 50% of
blood culture A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia ...
s yield any organisms. * Gonococcal arthritis – '' Neisseria gonorrhoeae'' is a common cause of septic arthritis in people who are sexually active and under 40 years old. The bacteria is spread through the blood to the joint following sexual transmission. Other symptoms of
disseminated gonococcal infection To disseminate (from lat. ''disseminare'' "scattering seeds"), in the field of communication, is to broadcast a message to the public without direct feedback from the audience. Meaning Dissemination takes on the theory of the traditional view ...
can include migration of joint pain, tenosynovitis and dermatitis. Synovial fluid cultures are positive in 25 to 70% of the cases while blood cultures are seldom positive. Apart from blood and joint cultures, swabs from
urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra ...
, rectum,
pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...
, and
cervix The cervix or cervix uteri (Latin, 'neck of the uterus') is the lower part of the uterus (womb) in the human female reproductive system. The cervix is usually 2 to 3 cm long (~1 inch) and roughly cylindrical in shape, which changes during ...
should also be taken.
Polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
(PCR) is another useful way of identifying gonococcal infections if diagnosis is difficult and clinical presentation is similar to
reactive arthritis Reactive arthritis, also known as Reiter's syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body (cross-reactivity). Coming into contact with bacteria and developing an infection can t ...
. * Others – Fungal and
mycobacterial ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') a ...
infections are rare causes of septic arthritis and usually have a slow onset of joint symptoms. Mycobacterial joint infection most commonly affects hip and knee joints, caused by reactivation of past mycobacterial infections, with or without signs and symptoms of tuberculosis in lungs. Synovial fluid cultures will be positive in 80% of the cases. However, acid fast smears are not useful.
Histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures v ...
is not specific to myocobacterial infection as there are other
granulomatous disease A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectiou ...
s that can show similar histology. '' Borrelia burgdorferi'', a bacterium that causes
lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...
, can affect multiple large joints such as the knee. Confirmation of Lyme disease is done through
enzyme-linked immunosorbent assay The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
(ELISA) followed by confirmation using
Western Blot The western blot (sometimes called the protein immunoblot), or western blotting, is a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detect ...
test. It cannot be cultured from synovial fluid. However, PCR testing yields 85% positive result from synovial fluid. Viruses such as rubella, parvovirus B19,
chikungunya Chikungunya is an infection caused by the ''Chikungunya virus'' (CHIKV). Symptoms include fever and joint pains. These typically occur two to twelve days after exposure. Other symptoms may include headache, muscle pain, joint swelling, and a r ...
, and HIV infection can also cause septic arthritis. * Prosthetic joint infection – Artificial joint infection are usually caused by coagulase negative Staphylococci, ''Staphylococcus aureus'', and gram negative bacilli. Concurrent infections by multiple organisms is also reported in 20% of the cases. The risk factors of prosthetic joint infections are: previous fracture, seropositive
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...
, obesity, revision arthroplasty, and surgical site infections.


List of organisms

* '' Staphylococci'' (40%) ** '' Staphylococcus aureus'' – the most common cause in most age groups. Can be caused by skin infection, previously damaged joint, prosthetic joint or intravenous drug use. ** ''
coagulase-negative staphylococci ''Staphylococcus'' is a genus of Gram-positive bacteria in the family Staphylococcaceae from the order Bacillales. Under the microscope, they appear spherical (cocci), and form in grape-like clusters. ''Staphylococcus'' species are facultati ...
'' – usually due to prosthetic joint * ''
Streptococci ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occu ...
'' – the second-most common cause (28%) ** '' Streptococcus pyogenes'' – a common cause in children under 5 ** '' Streptococcus pneumoniae'' ** Group B streptococci – a common cause in infants * ''
Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bact ...
'' * '' Neisseria gonorrhoeae'' – the most common cause of septic arthritis in young, sexually active adults. Multiple macules or vesicles seen over the trunk are a pathognomonic feature.
* '' Neisseria meningitidis'' * ''
Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...
'' – in the elderly, IV drug users and the seriously ill * ''
Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. a ...
'' – IV drug users or penetrating trauma through the shoe * '' M. tuberculosis'', '' Salmonella spp.'' and '' Brucella spp.'' – cause septic spinal arthritis * ''
Eikenella corrodens ''Eikenella corrodens'' is a Gram-negative facultative anaerobic bacillus that can cause severe invasive disease in humans. It was first identified by M. Eiken in 1958, who called it ''Bacteroides corrodens''. ''E. corrodens'' is a rare pericar ...
'' –
human bite Biting is a common zoological behavior involving the active, rapid closing of the jaw around an object. This behavior is found in toothed animals such as mammals, reptiles, amphibians and fish, but can also exist in arthropods. Myocytic cont ...
s * '' Pasteurella multocida'', '' bartonella henselae'', '' capnocytophaga – animal bites or scratches * Fungal species – immunocompromised state * '' Borrelia burgdorferi'' – ticks, causes
lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...
* '' Spirillum minus'', ''
Streptobacillus moniliformis ''Streptobacillus moniliformis'' is a non-motile, Gram-negative rod-shaped bacterium that is a member of the family Leptotrichiaceae. The genome of ''S. moniliformis'' is one of two completed sequences of the order Fusobacteriales. Its name c ...
'' – rat bites


Diagnosis

Septic arthritis should be considered whenever a person has rapid onset pain in a swollen joint, regardless of fever. One or multiple joints can be affected at the same time. Laboratory studies such as blood cultures,
white blood cell count A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cells and ...
with differential, ESR, and CRP should also be included. However, white cell count, ESR, and CRP are nonspecific and could be elevated due to infection elsewhere in the body. Serologic studies should be done if
lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...
is suspected. Blood cultures can be positive in 25 to 50% of those with septic arthritis due to spread of infection from the blood. CRP more than 20 mg/L and ESR greater than 20 mm/hour together with typical signs and symptoms of septic arthritis should prompt
arthrocentesis Arthrocentesis, or joint aspiration, is the clinical procedure performed to diagnose and, in some cases, treat musculoskeletal conditions. The procedure entails using a syringe to collect synovial fluid from or inject medication into the joint caps ...
from the affected joint for
synovial fluid Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articul ...
examination. The synovial fluid should be collected before the administration of
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and preventio ...
and should be sent for gram stain,
culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups ...
, leukocyte count with differential, and crystal studies. This can include NAAT testing for ''
N. gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection g ...
'' if suspected in a sexually active person. In children, the
Kocher criteria The Kocher criteria are a tool useful in the differentiation of septic arthritis from transient synovitis in the child with a painful hip. They are named for Mininder S. Kocher, an orthopaedic surgeon at Boston Children's Hospital and Professor o ...
is used for diagnosis of septic arthritis.


Differential diagnosis

The differential diagnosis of septic arthritis is broad and challenging. First, it has to be differentiated from acute hematogenous osteomyelitis. This is because the treatment lines of both conditions are not identical. Noteworthy, septic arthritis and acute hematogenous osteomyelitis can co-occur. Especially in the hip and shoulder joints their co-occurrence is likely and represents a diagnostic challenge. Therefore, physicians should have a high suspicion index in that regard. This is because in both the hip and shoulder joints the metaphysis is intra-articular which in turn facilitates the spread of hematogenous osteomyelitis into the joint cavity. Conversely, joint sepsis may spread to the metaphysis and induce osteomyelitis. Acute exacerbation of juvenile idiopathic arthritis and transient synovitis of the hip both of which are non-septic conditions may mimic septic arthritis. More serious and life-threatening disorders as bone malignancies e.g. Ewing sarcoma and osteosarcoma may mimic septic arthritis associated with concurrent acute hematogenous osteomyelitis. In this regard, Magnetic resonance imaging may play an important role in the differential diagnosis.


Joint aspiration

In children, joint synovial fluid aspiration techniques aim at isolating the infectious organism by culture and sensitivity analysis. Cytological analysis of the joint aspirate can point to septic arthritis. However, a negative culture and sensitivity test does not rule out the presence of septic arthritis. Various clinical scenarios and technique-related factors may impact the validity of results of the culture and sensitivity. Additionally, results of cytological analysis, though important, should not be interpreted in isolation of the clinical settings. In the joint fluid, the typical white blood cell count in septic arthritis is over 50,000–100,000 cells per 10−6/l (50,000–100,000 cell/ mm3); where more than 90% are neutrophils is suggestive of septic arthritis. For those with prosthetic joints, white cell count more than 1,100 per mm3 with neutrophil count greater than 64% is suggestive of septic arthritis. However, septic
synovial fluid Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articul ...
can have white blood cell counts as low as a few thousand in the early stages. Therefore, differentiation of septic arthritis from other causes is not always possible based on cell counts alone. Synovial fluid PCR analysis is useful in finding less common organisms such as '' Borrelia'' species. However, measuring protein and glucose levels in joint fluid is not useful for diagnosis. The Gram stain can rule in the diagnosis of septic arthritis, however, cannot exclude it.
Synovial fluid Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articul ...
cultures are positive in over 90% of nongonoccocal arthritis; however, it is possible for the culture to be negative if the person received antibiotics prior to the joint aspiration. Cultures are usually negative in gonoccocal arthritis or if fastidious organisms are involved. If the culture is negative or if a gonococcal cause is suspected, NAAT testing of the synovial fluid should be done. Positive crystal studies do not rule out septic arthritis. Crystal-induced arthritis such as
gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intens ...
can occur at the same time as septic arthritis. A lactate level in the synovial fluid of greater than 10 mmol/L makes the diagnosis very likely.


Blood tests

Laboratory testing includes
white blood cell count A complete blood count (CBC), also known as a full blood count (FBC), is a set of medical laboratory tests that provide information about the cells in a person's blood. The CBC indicates the counts of white blood cells, red blood cells and ...
, ESR and CRP. These values are usually elevated in those with septic arthritis; however, these can be elevated by other infections or inflammatory conditions and are, therefore, nonspecific.
Procalcitonin Procalcitonin (PCT) is a peptide precursor of the hormone calcitonin, the latter being involved with calcium homeostasis. It arises once preprocalcitonin is cleaved by endopeptidase. It was first identified by Leonard J. Deftos and Bernard A. Ro ...
may be more useful than CRP.
Blood culture A blood culture is a medical laboratory test used to detect bacteria or fungi in a person's blood. Under normal conditions, the blood does not contain microorganisms: their presence can indicate a bloodstream infection such as bacteremia ...
s can be positive in up to half of people with septic arthritis.


Imaging

Imaging such as
x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
, CT, MRI or
ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...
are nonspecific. They can help determine areas of inflammation but cannot confirm septic arthritis. When septic arthritis is suspected,
x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s should generally be taken. This is used to assess any problems in the surrounding structures such as bone fractures, chondrocalcinosis, and inflammatory arthritis which may predispose to septic arthritis. While x-rays may not be helpful early in the diagnosis/treatment, they may show subtle increase in joint space and tissue swelling. Later findings include joint space narrowing due to destruction of the joint.
Ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...
is effective at detecting joint effusions. CT and MRI are not required for diagnosis; but if the diagnosis is unclear or the joints are hard to examine (ie. sacroiliac or hip joints); they can help to assess for inflammation/infection in or around the joint (i.e. Osteomyelitis), bone erosions, and bone marrow oedema. Both CT and MRI scans are helpful in guiding
arthrocentesis Arthrocentesis, or joint aspiration, is the clinical procedure performed to diagnose and, in some cases, treat musculoskeletal conditions. The procedure entails using a syringe to collect synovial fluid from or inject medication into the joint caps ...
of the joints.


Differential diagnosis

* Crystal induced arthritis such as
gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of a red, tender, hot and swollen joint, caused by deposition of monosodium urate monohydrate crystals. Pain typically comes on rapidly, reaching maximal intens ...
or pseudogout * Inflammatory arthritis **
Rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...
** Seronegative spondyloarthropathy such as
ankylosing spondylitis Ankylosing spondylitis (AS) is a type of arthritis characterized by long-term inflammation of the joints of the spine typically where the spine joins the pelvis. Occasionally areas affected may include other joints such as the shoulders or hi ...
or
reactive arthritis Reactive arthritis, also known as Reiter's syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body (cross-reactivity). Coming into contact with bacteria and developing an infection can t ...
* Traumatic arthritis due to hemarthrosis,
fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displ ...
or
foreign body A foreign body (FB) is any object originating outside the body of an organism. In machinery, it can mean any unwanted intruding object. Most references to foreign bodies involve propulsion through natural orifices into hollow organs. Foreign b ...
*
Osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the ...


Treatment

Treatment is usually with intravenous
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
s, analgesia and washout and/or aspiration of the joint. Draining the pus from the joint is important and can be done either by needle (
arthrocentesis Arthrocentesis, or joint aspiration, is the clinical procedure performed to diagnose and, in some cases, treat musculoskeletal conditions. The procedure entails using a syringe to collect synovial fluid from or inject medication into the joint caps ...
) or opening the joint surgically ( arthrotomy). Empiric antibiotics for suspected bacteria should be started. This should be based on Gram stain of the
synovial fluid Synovial fluid, also called synovia, elp 1/sup> is a viscous, non-Newtonian fluid found in the cavities of synovial joints. With its egg white–like consistency, the principal role of synovial fluid is to reduce friction between the articul ...
as well as other clinical findings. General guidelines are as follows: * Gram positive cocci
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
* Gram negative cocci
Ceftriaxone Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and join ...
* Gram negative bacilli
Ceftriaxone Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and join ...
,
cefotaxime Cefotaxime is an antibiotic used to treat a number of bacterial infections in human, other animals and plant tissue culture. Specifically in humans it is used to treat joint infections, pelvic inflammatory disease, meningitis, pneumonia, urinar ...
, or ceftazidime * Gram stain negative and immunocompetent –
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
* Gram stain negative and immunocompromised
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
+ third generation cephalosphorin * IV drug use (possible pseudomonas aeruginosa) – ceftazidime +/- an aminoglycoside Once cultures are available, antibiotics can be changed to target the specific organism. After a good response to intravenous antibiotics, people can be switched to oral antibiotics. The duration of oral antibiotics varies, but is generally for 1–4 weeks depending on the offending organism. Repeated daily joint aspiration is useful in the treatment of septic arthritis. Every aspirate should be sent for culture, gram stain, white cell count to monitor the progress of the disease. Both open surgery and arthroscopy are helpful in the drainage of the infected joint. During surgery, lysis of the adhesions, drainage of pus, and debridement of the necrotic tissues are done. Close follow up with physical exam & labs must be done to make sure the person is no longer feverish, pain has resolved, has improved range of motion, and lab values are normalized. In infection of a prosthetic joint, a
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular po ...
is often created on the surface of the prosthesis which is resistant to antibiotics. Surgical debridement 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. People that cannot have surgery may try long-term antibiotic therapy in order to suppress the infection. The use of prophylactic antibiotics before dental, genitourinary, gastrointestinal procedures to prevent infection of the implant is controversial. Low-quality evidence suggests that the use of
corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are inv ...
s may reduce pain and the number of days of antibiotic treatment in children.


Outcomes

Risk of permanent impairment of the joint varies greatly. This usually depends on how quickly treatment is started after symptoms occur as longer lasting infections cause more destruction to the joint. The involved organism, age, preexisting arthritis, and other comorbidities can also increase this risk. Gonococcal arthritis generally does not cause long term impairment. For those with ''Staphylococcus aureus'' septic arthritis, 46 to 50% of the joint function returns after completing antibiotic treatment. In pneumococcal septic arthritis, 95% of the joint function will return if the person survives. One-third of people are at risk of functional impairment (due to amputation, arthrodesis, prosthetic surgery, and deteriorating joint function) if they have an underlying joint disease or a synthetic joint implant. Mortality rates generally range from 10 to 20%. These rates increase depending on the offending organism, advanced age, and comorbidities such as
rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are inv ...
.


Epidemiology

In children and adolescence septic arthritis and acute hematogenous osteomyelitis occurs in about 1.34 to 82 per 100,000 per annual hospitalization rates. In adults septic arthritis occurs in about 5 people per 100,000 each year. It occurs more commonly in older people. With treatment, about 15% of people die, while without treatment 66% die.


References


External links

{{DEFAULTSORT:Septic Arthritis Arthritis Infectious arthropathies Medical emergencies Wikipedia medicine articles ready to translate Wikipedia emergency medicine articles ready to translate