Acute Infectious Arthritis

Gonococcal arthritis can cause a distinctive dermatitis-polyarthritis-tenosynovitis syndrome.

Classic manifestations are

Symptoms of the original mucosal infection (eg, urethritis, cervicitis) may not be present.

Nongonococcal bacterial arthritis causes progressive moderate to severe joint pain that is markedly worsened by movement or palpation. Most infected joints are swollen, red, and warm. Fever is absent or low grade in up to 50% of patients; only 20% of patients report a shaking chill. Virulent organisms (eg, S. aureus, Pseudomonas aeruginosa) generally cause a more fulminant arthritis, whereas less virulent organisms (eg, coagulase-negative staphylococci, Propionibacterium acnes) cause a less fulminant arthritis.

In 80% of adults, nongonococcal bacterial arthritis is monarticular and usually occurs in a peripheral joint: knee, hip, shoulder, wrist, ankle, or elbow. In children,≥ 90% is monarticular: knee (39%), hip (26%), and ankle (13%).

Polyarticular involvement is somewhat more common among patients who are immunosuppressed, who have an underlying chronic arthritis (eg, rheumatoid arthritis, osteoarthritis), or who have a streptococcal or staphylococcal infection (especially beta-hemolytic streptococcus or S. aureus). In injection drug users and patients with indwelling vascular catheters, axial joints (eg, sternoclavicular, costochondral, hip, shoulder, vertebral, symphysis pubis, sacroiliac) are often involved. H. influenza may cause a dermatitis-arthritis syndrome similar to gonococcal infection.

Infection due to human, dog, or cat bites (see Human and Mammal Bites Human and Mammal Bites Human and other mammal bites (mostly dog and cat bites, but also squirrel, gerbil, rabbit, guinea pig, and monkey bites) are common and occasionally cause significant morbidity and disability... read more ) usually develops within 48 hours.

Rat bites Rat-Bite Fever Rat-bite fever is caused by either Streptobacillus moniliformis or Spirillum minus. Symptoms of the streptobacillary form include fever, rash, and arthralgias. The spirillary form... read more cause systemic symptoms such as fever, rash, and joint pain or true arthritis with regional adenopathy within about 2 to 10 days.

Viral infectious arthritis sometimes causes symptoms similar to acute nongonococcal bacterial arthritis and is more likely to be polyarticular than bacterial arthritis.

Patients with B. burgdorferi arthritis may have other symptoms of Lyme disease Symptoms and Signs Lyme disease is a tick-transmitted infection caused by the spirochete Borrelia species. Early symptoms include an erythema migrans rash, which may be followed weeks to months later by... read more or present only with acute monarthritis or oligoarthritis, which, if untreated, may be recurrent. Chronic pain that remains after appropriate therapy is likely to be of noninfectious etiology.

A polyarticular rheumatoid arthritis–like syndrome is distinctly unusual and more likely to be from another diagnosis.

Synovial fluid examination is the cornerstone of diagnosis of acute joint infection. Fluid is examined grossly and sent for cell count and differential, Gram stain, aerobic and anaerobic culture, and crystals. Foul-smelling synovial fluid suggests anaerobic infection. Fluid from an acutely infected joint usually reveals a white blood cell (WBC) count > 20,000/mcL (sometimes > 100,000/mcL) consisting of > 95% polymorphonuclear leukocytes. WBC counts tend to be higher in nongonococcal bacterial than in gonococcal infectious arthritis. WBC counts may also be lower in early or partially treated infections.

Gram stain reveals organisms in only 50 to 75% of joints with acute bacterial arthritis, most often with staphylococci. If positive, Gram stain is suggestive, but cultures are definitive.

The presence of crystals does not exclude coexisting infectious arthritis. Initial synovial fluid analysis often cannot differentiate between infectious and other inflammatory synovial fluid. There is significant overlap between the synovial cell counts in fluids from patients with gout and infection. If differentiation is impossible by clinical means or synovial fluid examination, infectious arthritis is assumed, pending culture results. Inoculation of synovial fluid into aerobic blood culture bottles can improve detection of Kingella kingae.

Blood tests, such as blood cultures, complete blood count, and erythrocyte sedimentation rate (or C-reactive protein), are usually obtained. However, normal results do not exclude infection. Likewise, WBC count, erythrocyte sedimentation rate, or C-reactive protein may be increased in noninfectious joint inflammation (including gout) as well as infectious joint inflammation. The serum urate level should not be used to diagnose or exclude gout as the cause of the arthritis, because the level can be normal or even low in gout, and may be high, although unrelated to gout, with an acute bacterial infection.

Molecular testing (eg, polymerase chain reaction) may be used to directly detect organisms in clinical specimens. Gonococci may be detected with nucleic acid amplification testing (NAAT) of specimens from the cervix, urethra, oropharynx, or rectum. Some difficult to cultivate organisms, such as Mycobacterium tuberculosis and Tropheryma whipplei, may be directly detected in synovial fluid using NAAT.

Plain x-rays of the involved joint are not diagnostic of acute infection but can exclude other conditions sometimes under consideration (eg, fractures). Abnormalities in early acute bacterial arthritis are limited to soft-tissue swelling and signs of synovial effusions. After 10 to 14 days of untreated bacterial infection, destructive changes of joint space narrowing (reflecting cartilage destruction) and erosions or foci of subchondral osteomyelitis may appear. Gas visible within the joints suggests infection with Escherichia coli or anaerobes.

MRI is considered if the joint is not easily accessible for examination and aspiration (eg, an axial joint). MRI or ultrasonography can identify sites of effusion or abscess that can be aspirated or drained for both diagnosis and therapy. MRI can provide early suggestion of associated osteomyelitis. Bone scans using technetium-99m can be falsely negative in infectious arthritis. Also, because they show increased uptake with increased blood flow in inflamed synovial membranes and in metabolically active bone, they can be falsely positive in noninfectious inflammatory arthritis such as gout. Nuclear imaging and MRI do not distinguish infection from crystal-induced arthritis Overview of Crystal-Induced Arthritides Arthritis can result from intra-articular deposition of crystals: Monosodium urate Calcium pyrophosphate dihydrate Basic calcium phosphate (apatite) Rarely, others such as calcium oxalate crystals read more .

If gonococcal arthritis is suspected, blood and synovial fluid samples should be immediately plated on nonselective chocolate agar, and specimens from the urethra, endocervix, rectum, and pharynx should be plated on selective Thayer-Martin medium. The nucleic acid–based tests often used to diagnose genital gonococcal infection are done on synovial fluid only in specialized laboratories. Genital cultures or DNA testing is also done. Blood cultures may be positive during the first week and may assist in microbiologic diagnosis.

Synovial fluid cultures from joints with frank purulent arthritis are usually positive, and fluid from skin lesions may be positive. If disseminated gonococcal infection is suspected based on clinical criteria, it is assumed to be present even if all gonococcal cultures are negative. Clinical response to antibiotics (anticipated within 5 to 7 days) can help confirm the diagnosis of gonorrhea Diagnosis Gonorrhea is caused by the bacterium Neisseria gonorrhoeae. It typically infects epithelia of the urethra, cervix, rectum, pharynx, or conjunctivae, causing irritation or pain and purulent... read more .

Initial antibiotic selection is directed at the most likely pathogens. The regimen is adjusted based on the results of culture and susceptibility testing.

Gonococcal arthritis is treated with

IV ceftriaxone is continued until at least 24 hours after symptoms and signs resolve, followed by cefixime 400 mg orally 2 times a day for 7 days if the organism is proved susceptible. Consult an infectious disease specialist if the patient does not improve on this regimen or cannot tolerate cephalosporins. In such cases, alternative regimens may include azithromycin plus either gemifloxacin or gentamicin. Ciprofloxacin 750 mg orally 2 times a day may be used only if the organism is isolated and proved susceptible. Any coexisting genital infection with C. trachomatis will be adequately treated by the initial dose of azithromycin.

If nongonococcal gram-positive infection is suspected by Gram stain in an adult, or if no organisms are seen, treatment is with:

However, because methicillin resistance is now common in community-acquired S. aureus, for patients with gram-positive cocci in clusters on gram stain or a negative gram stain when S. aureus is suspected, vancomycin is the empiric choice.

If gram-negative infection is suspected (eg, in patients with immunosuppression or serious comorbid disorders, injection drug use, a recent infection with antibiotic use, or an indwelling vascular catheter), empiric treatment includes a parenteral 3rd-generation cephalosporin with antipseudomonal activity (eg, ceftazidime 2 g IV every 8 hours) and, if infection is severe, an aminoglycoside.

Neonates should be treated initially with an antibiotic that covers gram-positive infection (eg, nafcillin, vancomycin) plus an antibiotic that covers gram-negative infection (eg, gentamicin or a 3rd-generation cephalosporin such as cefotaxime).

Children > 3 months of age should be treated initially similarly to adults.

Parenteral antibiotics are continued until clinical improvement is clear (usually 2 to 4 weeks), and oral antibiotics should be given at high doses for another 2 to 6 weeks according to the clinical response.

Infections caused by streptococci and Haemophilus are usually eradicated after 2 weeks of oral antibiotics after IV treatment.

Staphylococcal infections are treated with antibiotics for at least 3 weeks and often 6 weeks or longer, especially in patients with prior arthritis in the affected joint, immunosuppression, or whose diagnosis was delayed.

In addition to antibiotics, acute nongonococcal bacterial arthritis requires large-bore needle aspiration of intra-articular pus at least once a day, or tidal irrigation lavage, arthroscopic lavage, or arthrotomy for debridement. Joints affected with rheumatoid arthritis should generally undergo early and aggressive surgical debridement and drainage.

For gonococcal arthritis with persistent effusion, pus is aspirated and drainage may need to be repeated as necessary.

Acute bacterial arthritis requires joint splinting for the first few days to reduce pain, followed by passive and active range-of-motion exercises to limit contractures, with muscle strengthening as soon as it can be tolerated. NSAIDs (nonsteroidal anti-inflammatory drugs) can help decrease pain and inflammation once a diagnosis is confirmed. Intra-articular corticosteroids should be avoided during the acute infection. Because bacteriologic tests may be falsely negative, potent anti-inflammatory therapy should generally be avoided until a bacterial source has been definitively excluded. Opioids can be used for pain control.

Viral arthritis is treated supportively.

Bite wounds are treated with antibiotics and surgical drainage as necessary (see treatment of human and mammal bites Treatment Human and other mammal bites (mostly dog and cat bites, but also squirrel, gerbil, rabbit, guinea pig, and monkey bites) are common and occasionally cause significant morbidity and disability... read more ).