AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Septic arthritis, also known as infectious arthritis, may represent a direct invasion of joint space by various microorganisms, including bacteria, viruses, mycobacteria, and fungi. Reactive arthritis, a sterile inflammatory process, may be the consequence of an infectious process located elsewhere in the body. Although any infectious agent may cause arthritis, bacterial pathogens are the most significant because of their rapidly destructive nature. For this reason, the current discussion concentrates on bacterial septic arthritides. Failure to recognize and to appropriately treat septic arthritis results in significant rates of morbidity and may even lead to death.

Because of the increasing use of prosthetic joints, infection associated with these devices may be the most common and challenging type of septic arthritis encountered by most clinicians.¹

Approximately 20,000 cases of septic arthritis occur in the United States each year. The 2 major classes of bacterial/suppurative arthritis are gonococcal and nongonococcal.^{1, 2, 3, 4} Overall, although Neisseria gonorrhoeae remains the most common pathogen (75% of cases) among younger sexually active individuals,^{5, 6} Staphylococcus aureus infection is the cause of the vast majority of cases of acute bacterial arthritis in adults and in children older than 2 years.⁷ This pathogen is the cause in 80% of infected joints affected by rheumatoid arthritis.

Streptococcal species, such as Streptococcus viridans, Streptococcus pneumoniae,^{8, 9} and group B streptococci, account for 20% of cases. Aerobic gram-negative rods are involved in 20-25% of cases. Most of these infections occur in people who are very young, who are very old,¹⁰ who are immunosuppressed, and who abuse intravenous drugs.¹ Infection of the sternoclavicular and sacroiliac joints with Pseudomonas aeruginosa or Serratia species occurs almost exclusively in persons who abuse intravenous drugs. Persons with leukemia are predisposed to Aeromonas infections.¹¹

Polymicrobial joint infections (5-10% of cases) and infection with anaerobic organisms (5% of cases) are usually a consequence of trauma or abdominal infection. The organism of Lyme disease (ie, Borrelia burgdorferi), a large variety of viruses (eg, HIV, lymphocytic choriomeningitis virus, hepatitis B virus, rubella virus), mycobacteria, fungi (eg, Histoplasma species, Sporothrix schenckii, Coccidioides immitis, Blastomyces species), and other pathogens may produce nonsuppurative joint infection.¹²

Three major types of prosthetic joint infections (PJIs) exist: those that occur early, within 3 months of implantation; those that are delayed, within 3-24 months of implantation; and those that occur later than 24 months following the implantation. Most cases of early PJI are caused by S aureus, while delayed infections are due to coagulase-negative S aureus (CONS) and gram-negative aerobes. Both of these types are acquired in the operating room. Late cases of PJI are secondary to hematogenous spread from various infectious foci.¹³

Pathophysiology

Organisms may invade the joint by direct inoculation, by contiguous spread from infected periarticular tissue, or via the bloodstream (the most common route).¹¹

The normal joint has several protective components. Healthy synovial cells possess significant phagocytic activity, and synovial fluid normally has significant bactericidal activity. Rheumatoid arthritis and systemic lupus erythematosus hamper the defensive functions of synovial fluid and decrease chemotaxis and phagocytic function of polymorphonuclear leukocytes.

Previously damaged joints, especially those damaged by rheumatoid arthritis, are the most susceptible to infection. The synovial membranes of these joints exhibit neovascularization and increased adhesion factors; both conditions increase the chance of bacteremia, resulting in a joint infection. Some microorganisms have properties that promote their tropism to the synovium. S aureus readily binds to articular sialoprotein, fibronectin collage, elastin, hyaluronic acid, and prosthetic material via specific tissue adhesion factors (microbial surface components recognizing adhesive matrix molecules [MSCRAMMs]). In adults, the arteriolar anastomosis between the epiphysis and the synovium permits the spread of osteomyelitis into the joint space.

The major consequence of bacterial invasion is damage to articular cartilage. This may be due to the particular organism's pathological properties, such as the chondrocyte proteases of S aureus, as well as to the host's polymorphonuclear leukocytes response. The cells stimulate synthesis of cytokines and other inflammatory products, resulting in the hydrolysis of essential collagen and proteoglycans. Infection with N gonorrhoeae induces a relatively mild influx of WBCs into the joint, explaining, in part, the minimal joint destruction observed with infection with this organism compared to destruction associated with S aureus infection.

As the destructive process continues, pannus formation begins and cartilage erosion occurs at the lateral margins of the joint. Large effusions, which can occur in infections of the hip joint, impair the blood supply and result in aseptic necrosis of bone. These destructive processes are well advanced as early as 3 days into the course of untreated infection.

Viral infections may cause direct invasion (rubella) or production of antigen/antibody complexes. Such immunological mechanisms occur in infections with hepatitis B, parvovirus B19, and lymphocytic choriomeningitis viruses.¹²

Reactive, or postexposure, arthritis is observed more commonly in patients with human lymphocyte antigen B27 (HLA-B27) histocompatibility antigens. Although various infections can cause reactive arthritis, gastrointestinal processes are by far the most common. Gastrointestinal pathogens associated with reactive arthritis include the following:

• Salmonella enteritidis
• Salmonella typhimurium
• Yersinia enterocolitica
• Campylobacter jejuni
• Clostridium difficile
• Shigella sonnei
• Entamoeba histolytica
• Cryptosporidium

Genitourinary infections, especially those due to Chlamydia trachomatis, are the second most common cause of reactive arthritis. The arthritis of Lyme disease usually results from immunological mechanisms, with a minority of cases due to direct invasion by an organism.

PJIs may be a consequence of local infection, such as intraoperative contamination (60-80% of cases), or of bacteremias (20-40% of cases).¹ The latter type may be spontaneous (ie, gingival disease) or secondary to various manipulations. Delayed wound healing is a major factor behind early PJI. Until the fascia has healed, the usual tissue barriers to infection of the implant are not present. Eventually, the implanted hardware becomes less susceptible to infection by hematogenous spread because the pseudocapsule develops around it.

The biofilm of CONS protects the pathogen from the host's defenses, as well as from various antibiotics. Polymethylmethacrylate cement inhibits WBC and complement function.

Overall, the most common organisms of PJIs are CONS (22% of cases) and S aureus (22% of cases). Enteric gram-negative organisms account for 25% of isolates. Streptococci, including S viridans, enterococci, and the beta-hemolytic streptococci, cause 21% of cases. Anaerobes are isolated from 10% of patients.

Frequency

United States

Approximately 20,000 cases of septic arthritis occur each year in the United States (7.8 cases per 100,000 person-years).⁴ The incidence of arthritis due to disseminated gonococcal infection is 2.8 cases per 100,000 person-years. Septic arthritis is becoming increasingly common among people who are immunosuppressed and elderly persons; these groups are more likely to have various comorbid disease states. The incidence of PJI among all prosthesis recipients ranges from 2-10%.

International

The incidence of septic arthritis in Europe is identical to that in the United States.

Mortality/Morbidity

The primary morbidity of septic arthritis is significant dysfunction of the joint, even if treated properly. The mortality rate depends primarily on the causative organism. N gonorrhoeae septic arthritis carries an extremely low mortality rate, while that of S aureus can approach 50%.¹⁴

Race

Septic arthritis has no recognized racial predisposition.

Sex

Fifty-six percent of patients with septic arthritis are male.

Age

Forty-five percent of people with septic arthritis are older than 65 years.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Because joint infections are uncommon, be especially attentive to features of the patient's history that may indicate an infectious process instead of a primary rheumatologic or orthopedic process.³

• Pay attention to the following symptoms:
• • Acuteness of onset of the joint pain
  • Whether the pain is superimposed on chronic pain
  • Previous history of joint disease or trauma, whether accidental or iatrogenic (eg, infection complicates 0.4% of arthrocenteses)
  • Whether the process is monoarticular or polyarticular and which joints are involved
  • The presence of extra-articular symptoms
  • Whether the patient has had vascular invasion due to catheterizations or intravenous drug abuse
• Obtain a thorough history regarding the possible presence of sexually transmitted diseases (STDs) or exposure to ticks (Lyme disease). The increase of group B streptococcal joint infections is associated with the increased prevalence of diabetes and increasing life expectancy.
• Numerous conditions that adversely affect the host's defenses (eg, liver disease, diabetes mellitus, lymphoma, solid tumors, complement deficiencies [C7, C8], immunosuppressive drugs, hypogammaglobulinemia) are increasingly observed in patients with septic arthritis. Determine the possible contribution of these diseases to the clinical presentation.
• The most important historical feature is the existence of underlying joint disease, especially rheumatoid arthritis. In addition, the possibility of recent injury to the joint or penetrating or blunt trauma must be explored. Ask the patient about needle aspiration of the joint or injections of corticosteroids into the joint. Elicit a history of diarrheal disease. Patients with an infected joint typically present with the triad of fever (40-60% of cases), pain (75% of cases), and impaired range of motion. These symptoms may evolve over a few days to a few weeks. Fever usually is low-grade (<102°F), with rigors present in only 20% of cases. Spiking fevers and chills are much more common with crystalline arthritis.
• Months after infection onset, 60% of patients with untreated Lyme disease develop swelling and pain, chiefly affecting the large joints. Usually, Lyme disease affects 1-2 joints at a time, with the knee involved most commonly. The distinguishing pattern is attacks extending from a few weeks to months and separated by periods of complete remission. The rate of recurrence lessens by about 15% per year. A small percentage of individuals develop chronic arthritis (ie, inflammation of a joint lasting ³1 y). This type of relapsing course almost always precedes the chronic stage of Lyme arthritis.
• Compared with patients with infections of native joints, most patients with PJI exhibit a prolonged low-grade course with gradually increasing pain.
• • Usually, no significant fever or swelling occurs (delayed PJI). However, individuals with early PJI present with an acute illness characterized by high-grade fever, focal swelling, and redness. Cellulitis and draining sinus tracts often develop.
  • Because late PJI is usually secondary to bacteremia, the clinical picture is often dominated by the source of the bloodstream infection.
  • The nature of the invading organism, the type of tissue infected, and the route of infection determine presentation. Thus, a high index of suspicion is needed for identification of bacteremic and delayed PJI. Because of its many pathogenic mechanisms, S aureus is usually associated with a fulminant course, as opposed to the indolent course of CONS that dominates delayed PJI. Relatively devitalized tissues (eg, wound hematomas) are conducive to rapid bacterial replication and a more acute course. Bacteremic spread allows infection with fewer organisms and leads to a more muted course.
• Reactive arthritis usually begins several weeks after the underlying infection has resolved. Few concurrent systemic symptoms occur.
• Symptoms of tuberculous arthritis are quite indolent; the diagnosis may be delayed for several years. Usually, the purified protein derivative (PPD) results are negative, and no signs, past or present, of pulmonary tuberculous exist.

Clinical Features of Viral Septic Arthritis

Physical

The most commonly involved joint is the knee (50% of cases), followed by the hip (20%), shoulder (8%), ankle (7%), and wrists (7%). The elbow, interphalangeal, sternoclavicular, and sacroiliac joints each make up 1-4% of cases. A thorough inspection of all joints for signs of erythema, swelling (90% of cases), warmth, and tenderness is essential for diagnosing infection. Infected joints usually exhibit an obvious effusion, which is associated with marked limitation of both active and passive ranges of motion. Frequently, these findings are apparent but may be diminished or poorly localized in cases of infection of the spine, hip, and shoulder joints.¹²

Signs and symptoms of infection may be muted in people who are elderly, who are immunocompromised (especially those with rheumatoid arthritis), and who abuse intravenous drugs.

• The pattern of joint involvement is an extremely important diagnostic feature. Of cases of nongonococcal suppurative arthritis, 85-90% are monoarticular. If the disease affects more than one joint, S aureus is most commonly implicated. Polyarticular arthritis is usually observed in gonococcal disease, various viral infections, Lyme disease, reactive arthritis, and various noninfectious processes.
• Group B streptococci most commonly infect the sacroiliac and sternoclavicular joints.
• Gonococcal musculoskeletal involvement may present in one of two ways.
• • Fever, arthralgias of multiple joints, and multiple skin lesions (dermatitis-arthritis syndrome) characterize disease that develops soon after the gonococcus disseminates from the cervix, urethra, or pharynx. Usually, this disease exhibits no clinical direct joint findings, but the process is one of tenosynovitis of asymmetric distribution. Typically, hand joints are involved most often, as well as those of the knee, wrist, ankle, and elbow. Skin lesions are multiple but seldom number more than 12, while lesions associated with meningococcemia may number more than 100. The lesions evolve over a few days from papular to pustular or vesicular to necrotic. This course may recur for several months. Findings on cultures of blood and mucosal surfaces are often positive; findings on cultures of joint fluid are usually negative. Sixty percent of disseminated gonococcal infections are of this type.
  • Monoarticular arthritis without associated systemic symptoms, tenosynovitis, or skin lesions characterizes disease that begins later after gonococcal dissemination than does dermatitis arthritis syndrome.⁶ Dermatitis-arthritis syndrome may or may not precede this phase. In a joint infected by the Lyme organism, swelling may be disproportionate to the level of pain. Baker cysts are a frequent feature of this type of infectious arthritis. Because the pain of an infected hip joint may not be localized directly and swelling of the joint is inconspicuous, perform specific maneuvers, such as the Fabere maneuver. Infection of the sacroiliac joint often presents as buttock, hip, or anterior thigh pain. Direct pressure usually elicits tenderness in the joint. Alternatively, hyperextension of the hip and leg while the patient is lying down (ie, Gaenslen maneuver) elicits pain in a suppurative sacroiliac joint.
• Septic bursitis most commonly involves the olecranon and prepatellar bursae. Swelling and pain are present. However, an infected bursa does not limit the range of motion of the underlying joint the way an actual joint infection does.¹⁵
• Physical findings are usually minimal in an infection of the prosthetic joint, and swelling is usually slight. The most distinctive finding is a draining sinus presumed to originate in the underlying infected prosthetic joint.
• Most cases of reactive arthritis involve a few large joints in an asymmetric fashion.
• Viral arthritis usually exhibits symmetric involvement of the smaller joints, especially the hands, with a concurrent rash.
• The joints of tuberculous arthritis can appear to be boggy on palpation.

Causes

Other distinctive host and/or situation-pathogen associations have been described, including Pasteurella multocida, Capnocytophaga species (dog and cat bites), Eikenella corrodens, anaerobes (especially Fusobacterium nucleatum and streptococcal species [human bites]), Aeromonas hydrophila (myelogenous leukemia), S aureus, CONS, gram-negative bacteria (prosthetic joints), P aeruginosa, Serratia species, Candida species (particularly common in persons who abuse intravenous drugs), Mycobacterium marinum (water exposure), S schenckii (gardening), and S pneumoniae (sickle cell anemia).

Unlike osteomyelitis, Salmonella species are not associated with the septic arthritis of sickle cell anemia. Ten to 30% of patients with brucellosis have lumbosacral spine involvement.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Primary rheumatological disorders - Vasculitis, crystalline arthritides
Drug-induced arthritis
Reactive arthritis - Postinfectious diarrhea syndrome, postmeningococcal and postgonococcal arthritis, arthritis of intrinsic bowel disease¹²

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Normal joint fluid is clear and colorless and produces a stringlike structure when ejected from a syringe, indicating normal viscosity. Infected joint fluid is typically yellow-green due to elevated levels of nucleated cells. An evaluation of the synovial fluid (ie, via leukocyte count, appearance on Gram stain, polarizing microscopy examination, culture) is the most rewarding approach in assessing a potentially infected joint. Additional stains and/or cultures should be obtained depending on the differential diagnoses considered.^{7, 16}
• Culture of the synovial fluid or of synovial tissue itself is the only definitive method of diagnosing septic arthritis. Culture results in patients with nongonococcal septic arthritis are almost always positive unless the patient has received antibiotics prior to the joint aspiration. Cultures of the joint fluid in gonococcal infections yield positive results in only about 25% of cases. The effectiveness of standard culture techniques is much more limited in patients with PJI.
• Therapeutic decisions cannot be delayed until results of the culture are available. An approach to rapid evaluation of an acutely inflamed joint is to screen the fluid for crystals via polarizing microscopy and for organisms via Gram stain (63-96% sensitive). If crystals are present and the Gram stain findings are negative, treatment for crystal-associated arthritis should be initiated. However, an exception to this would be the presence of significant risk factors for infection (eg, the focus of infection lies somewhere that could lead to bacteremia, such as pneumonia or pyelonephritis).
• If microscopy demonstrates no crystals, treat the patient for presumed infection even if the Gram stain findings are negative. The Gram stain is less than 60% sensitive for detection of bacteria in synovial fluid. Always send the fluid for culture, regardless of the result of the screening evaluation. A joint damaged by gout or pseudogout is prone to be infected. Culture of synovial tissue is indicated primarily to detect mycobacteria or fungi.
• If the patient's condition does not improve significantly after 5 days, the joint must be reaspirated and examined. Most septic joints have a WBC count that exceeds 50,000/μL, with more than 75% polymorphonuclear leukocytes. However, various sterile inflammatory processes may exhibit the same cellular profile.
• Findings from examination of the synovial fluid in Lyme arthritis are similar to those found in infection caused by any other type of bacterium. Positive serology results (ie, antibody measurements, Western blot, polymerase chain reaction [PCR] for Lyme disease) do not establish the diagnosis of Lyme arthritis. A positive result on any of these tests simply indicates that the patient has encountered B burgdorferi; a positive result does not necessarily establish a connection between the patient's musculoskeletal symptoms and Lyme disease.
• Alterations in the glucose and protein concentration of the synovial fluid are nonspecific; these should not be measured routinely.
• Obtain at least 2 sets of blood cultures to rule out a bacteremic origin of the septic joint.
• In the setting of possible gonococcal infection, obtaining cultures from the patient's rectum, cervix, urethra, and pharynx and from any skin lesions is most helpful. Immediate plating of the joint fluid directly onto appropriate media and/or rapid delivery of the specimen to the laboratory for appropriate plating and culturing are of benefit in improving the relatively low yield.¹⁷
• PCR holds promise for detection of bacterial DNA in joint fluid and synovial tissue. PCR has led to diagnosis of infective arthritis due to Yersinia species, B burgdorferi, Chlamydia species, N gonorrhoeae, and Ureaplasma species. Caveats concerning this approach are raised because it cannot be used to distinguish between live and dead organisms and it is susceptible to contamination. PCR also techniques hold some promise in detecting pathogens in patients who have recently received antibiotics. Unfortunately, many patients receive empirically administered antibiotics prior to the collection of synovial fluid.
• Silver stains can be used to detect organisms in 5% of cases of Lyme arthritis.
• Evaluation of a possibly infected prosthetic joint is similar to that of a natural joint.^{1, 18} The presence of leukocytes in the aspirated fluid is variable. Because many of the potential pathogens are also classic contaminating organisms (eg, CONS, Propionibacterium species, Corynebacterium species), repeat aspirates are often required to confirm the diagnosis. The use of multiple types of media with prolonged incubation times may increase both the sensitivity and specificity of the culture in PJI. The sensitivity of periprosthetic-tissue culture ranges from 65-94%.¹⁵ Material from fistulous tracts is associated with a high rate of contamination and is probably best avoided.
• At times, imaging studies may be required to determine the significance of a given culture (see Imaging Studies).
• The synovial fluid of reactive arthritis demonstrates few signs of inflammation. PCR may reveal DNA of the purported causative organism.
• The synovial fluid of a joint infected with Mycobacterium tuberculosis shows marked leukocytosis. Findings on acid-fast stains are usually negative. Culture results are positive in 80% of cases. Culture results of synovial biopsies are positive in 94% of specimens.
• The fluid of an infected bursa closely resembles that of a bacterial joint infection.¹³
• An elevated sedimentation rate or C-reactive protein is useful in following response to therapy, as well as in detecting an acute process in chronically affected joints.
• Measurement of serum uric acid levels cannot be used to establish or negate the diagnosis of uric acid arthropathy. Values may range widely during an acute attack.
• Appropriate serological tests for the diagnosis of various vasculitides or rheumatological disorders are often indicated.¹⁹

Imaging Studies

• Plain radiography is of limited value in evaluating a joint for infection.¹⁴
• • Periarticular soft-tissue swelling is the most common finding. Radiography is most useful in ruling out underlying osteomyelitis or periarticular osteomyelitis caused by the joint infection itself.
  • Plain radiography can reveal the linear deposition of calcium pyrophosphate. The radiographic findings of reactive arthritis are usually limited to those of soft-tissue swelling. Periarticular osteoporosis may be detected.
• Ultrasonography may be used to diagnose effusions in chronically distorted joints (secondary to trauma or rheumatoid arthritis).
• CT scans and MRIs are more sensitive for distinguishing osteomyelitis, periarticular abscesses, and joint effusions. The information gained usually does not justify the increased cost; however, these tests are most helpful in patients with sacroiliac or sternoclavicular joint infection to rule out extension into the mediastinum or pelvis. MRI is preferred because of its greater ability to image soft tissue.
• Radionuclide scans (ie, technetium Tc 99m, gallium Ga 67, indium In 111 leukocyte scans) are used to nonspecifically localize areas of inflammation. They cannot be used to distinguish infectious from sterile processes. However, they may be of use in diagnosing septic arthritis in relatively sequestered areas, such as the hip and sacroiliac joints.
• In PJI, plain radiography can reveal new subperiosteal bone growth and transcortical sinus tracts.¹ These findings are specific for infection. Arthrography can demonstrate loosening of the prosthesis and abscesses. Nuclear scans of all types are of limited diagnostic use in patients with PJI. CT scans are useful in ascertaining the state of the surrounding soft tissue. MRIs are limited by the type of implanted material. This diagnostic modality can safely image only titanium or tantalum devices.

Other Tests

Sonication of removed prosthetic material appears to increase the sensitivity of culture, especially in patients who have received antibiotics prior to surgery. 

Procedures

• Always perform joint aspiration under the most sterile conditions possible to prevent the introduction of infection.
• Obtaining a biopsy of the synovium may be necessary to diagnose one of the many causes (ie, mycobacterial, fungal) of granulomatous synovitis.

Histologic Findings

Examining the synovium histologically often establishes a diagnosis of fungal or mycobacterial joint infections.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

Medical management of infective arthritis focuses on adequate and timely drainage of the infected synovial fluid, administration of appropriate antimicrobial therapy, and immobilization of the joint to control pain. Acute PJI (<3 wk in duration) can be cured medically if it is of the early type or secondary to hematogenous spread without any evidence of periarticular soft-tissue involvement or joint instability.⁵

• In native joint infections, antibiotics usually need to be administered parenterally for at least 2 weeks. However, each case must be evaluated independently. Infection with either methicillin-resistant S aureus (MRSA) or methicillin-susceptible S aureus (MSSA) requires at least 4 full weeks of intravenous antibiotic therapy. Orally administered antimicrobial agents are almost never indicated in the treatment of S aureus infections. Gram-negative native joint infections with a pathogen that is sensitive to quinolones can be treated with oral ciprofloxacin for the final 1-2 weeks of treatment. As a rule, a 2-week course of intravenous antibiotics is sufficient to treat gonococcal arthritis.¹⁷
• Initial antibiotic choices must be empirical, based on the sensitivity pattern of the pathogens of the community. Consider the rise of resistance among potential bacteria when choosing an initial antibiotic regimen. If local incidence of MRSA is high (in particular, marked increase in the resistance of the pneumococcus), prescribe alternate antibiotics initially. Because many isolates of group B streptococci have become tolerant of penicillin, use a combination of penicillin and gentamicin or a later-generation cephalosporin. MRSA is becoming established outside of the hospital. Enterobacteriaceae and P aeruginosa are becoming more resistant to multiple antibiotics. Knowing the resistance patterns in the community, as well as in the hospital, is most important.
• Preferably, the antibiotic should be bactericidal with some effect against the slow-growing organisms that are protected within a biofilm (eg, CONS). Rifampin fulfills these requirements. It should never be used alone because of the rapid development of bacterial resistance to the drug.
• The choice of the type of drainage, whether percutaneous or surgical, has not been resolved completely.^{19, 20} In general, use a needle aspirate initially, repeating joint taps frequently enough to prevent significant reaccumulation of fluid. Aspirating the joint 2-3 times a day may be necessary during the first few days. If frequent drainage is necessary, surgical drainage becomes more attractive.
• If, after 5 days of therapy, the joint shows some degree of improvement, consider an empirical trial of an anti-inflammatory agent.
• If the joint fails to respond after 5 days of appropriate antibiotic therapy (eg, presence of clinically significant fever, continued synovial purulence, persistently positive findings on culture), reassess the therapeutic approach.
• Reculture the fluid and reexamine for crystals.
• Perform appropriate serologies for diagnosis of Lyme disease. If these are positive, treat per current guidelines.
• If fungal or mycobacterial infection is possible, consider obtaining a synovial biopsy.
• Consider the possibility of reactive arthritis. Nonsteroidal inflammatory agents are the primary therapeutic agents for reactive arthritis.
• Perform imaging studies, either radiographs or an MRI, to rule out periarticular osteomyelitis.
• The use of fluoroquinolones for an extended period should be considered when the removal of an infected prosthesis is not possible. Cure rates as high as 62% have been documented in relatively small series. Generally, such prolonged therapy is seen as suppressive and not curative.²¹

Surgical Care

Surgical drainage is indicated when one or more of the following occur: the appropriate choice of antibiotic and vigorous percutaneous drainage fails to clear the infection after 5-7 days, the infected joints are difficult to aspirate (eg, hip), or adjacent soft tissue is infected.

• Routine arthroscopic lavage is rarely indicated. However, drainage through the arthroscope is replacing open surgical drainage. With arthroscopic drainage, the operator can visualize the interior of the joint and can drain pus, debride, and lyse adhesions.
• Gonococcal-infected joints rarely require surgical drainage.
• In cases of PJI that require surgery for cure (see above), successful treatment requires appropriate antibiotic therapy combined with removal of the hardware. Despite appropriate antibiotic use, the success rate is only about 20% if the prosthesis is left in place. A 2-stage approach is the most effective technique.
• • First, remove the prosthesis and follow with 6 weeks of antibiotic therapy. Then, place the new joint, impregnating the methylmethacrylate cement with an anti-infective agent (ie, gentamicin, tobramycin). Antibiotic diffusion into the surrounding tissues is the goal. The success rate for this approach is approximately 95% for both hip and knee joints.
  • An intermediate method is to exchange the new joint for the infected joint in a 1-stage surgical procedure with concomitant antibiotic therapy. This method, with concurrent use of antibiotic cement, succeeds in 70-90% of cases.

Consultations

In general, obtain a consultation with an orthopedic surgeon or rheumatologist. If the initial treatment response is poor or the etiology of the synovitis remains unknown, consult with an infectious disease specialist.

Activity

If the patient's condition responds adequately after 5 days of treatment, begin gentle mobilization of the infected joint. Most patients require aggressive physical therapy to allow maximum postinfection functioning of the joint.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

The empirical choice of antibiotic therapy is based on results of the Gram stain and the clinical picture and background of the patient. When the Gram stain fails to reveal any microorganisms (40-50% of cases), the individual's age and sexual activity become the major determinants to differentiate gonococcal from nongonococcal arthritis. When no evidence suggests infection elsewhere, antibiotics must cover S aureus, streptococcal species, and gonococci (in patients who are sexually active).

Evidence shows that earlier initiation of an appropriate antibiotic regimen produces better functional results. Generally, treatment is administered intravenously for 3-4 weeks. The major exception to this is in the case of joints with gonococcal infection, for which total therapy is approximately 2 weeks, with switch to oral therapy. No indication exists for direct installation of antibiotics into the joint cavity. Such practice may increase the degree of inflammation.

Drug Category: Antibiotics

Therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting. The use of linezolid with or without rifampin should be considered for staphylococcal PJI.

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Usually, immobilization of the infected joint to control pain is not necessary after the first few days.
• Initial physical therapy consists of maintaining the joint in its functional position and providing passive range-of-motion exercises. The joint should bear no weight until the clinical signs and symptoms of synovitis have resolved. Aggressive physical therapy is often required to achieve maximum therapy benefit.
• Overall, the mean length of hospitalization for septic arthritis is 11.5 days. However, outpatient antibiotic therapy in stable patients can significantly reduce hospital stays.

Further Outpatient Care

• Perform physical therapy as indicated.

In/Out Patient Meds

• Oral antibiotics are usually used in treating gonococcal joint infections. Antibiotics have a role in suppressing associated chronic osteomyelitis and chronically infected prosthetic material that cannot be removed for various reasons.

Deterrence/Prevention

• Strictly adhere to sterile procedures whenever the joint space is invaded (eg, in aspiration or arthroscopic procedures).
• Antibiotic prophylaxis with an antistaphylococcal antibiotic has been demonstrated to reduce wound infections in joint replacement surgery. Polymethylmethacrylate cement impregnated with antibiotics may decrease perioperative infections.
• Using antibiotic prophylaxis on the same theoretical basis as that for cardiac valvular disease has been advocated. In short, whenever a sustained bacteremia may be encountered, consider using a prophylactic regimen similar to those of the American Heart Association. The implanted hardware most likely is at greatest risk of bacteremia infection within a few months of placement. The risk probably decreases as a pseudocapsule evolves. During this time, prophylaxis is probably most beneficial.
• Treat any infection promptly to lessen the chance of bloodstream invasion.
• Decreasing the incidence of underlying infections best prevents reactive arthritis.

Complications

• Dysfunctional joints, osteomyelitis, and sepsis are complications.

Prognosis

• Fifty percent of adults with septic arthritis have significant sequelae of decreased range of motion or chronic pain after infection.⁴
• Predictors of poor outcome in suppurative arthritis include the following:
• • Age older than 60 years
  • Infection of the hip or shoulder joints
  • Underlying rheumatoid arthritis
  • Positive findings on synovial fluid cultures after 7 days of appropriate therapy
  • Delay of 7 days or more in instituting therapy
• Thirty percent of cases of reactive arthritis may become chronic.

Patient Education

• Instruct patients with a prosthetic joint in place to recognize early signs of joint infection and, more importantly, to recognize bacterial infections in other parts of their bodies to prevent associated bacteremias.
• For excellent patient education resources, visit eMedicine's Arthritis Center and Bites and Stings Center. Also, see eMedicine's patient education articles Knee Pain and Ticks.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to recognize an infected joint and to promptly institute appropriate therapy poses a significant malpractice risk.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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Article Last Updated: Aug 25, 2008