Septic Arthritis Differential Diagnoses

Updated: Dec 09, 2022
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Diagnostic Considerations

Differential Diagnoses

When evaluating a patient with suspected septic arthritis, also consider conditions such as primary rheumatologic disorders (eg, vasculitis, crystalline arthritides), drug-induced arthritis, and reactive arthritis (eg, postinfectious diarrhea syndrome, postmeningococcal and postgonococcal arthritis, arthritis of intrinsic bowel disease). [2]

In early disseminated gonococcal infection, an early tenosynovitis predominates without actual joint invasion such as occurs in the later variety of disseminated gonococcal infection. A viral infection usually results in a polyarticular arthritis. Pustular lesions are consistent (as is almost any type of skin lesion) with staphylococcal bacteremia. Whenever vesicles are present, one needs to strongly consider staphylococcal infection.

Unlike salmonella osteomyelitis, the frequency of septic arthritis is not greatly increased in patients with sickle cell anemia. However, when septic arthritis does occur, Salmonella is more commonly identified.

Staphylococcus aureus remains the most common infectious agent in people who abuse intravenous drugs. However, a high rate of infections with gram-negative organisms, especially Pseudomonas aeruginosa and Serratia species, occurs in cases of septic arthritis. A higher rate of fungal and anaerobic infections has been documented. Unusual locations, such as the sternoclavicular joint, have more frequently been encountered.

The syndromic approach to the diagnosis of SA

The priority of the clinician is to recognize SA and to initiate appropriate therapy as soon as possible, so as to minimize the morbidity and mortality of the infection. With the proliferation of imaging studies and serologic testing, along with the increase of immunosuppressed patients and IVDA, the practitioner is more and more challenged to avoid basing a diagnosis solely on test result and/or imaging studies. These findings must be validated with a compatible history/symptoms and physical examination. A disease represents a grouping of signs (physical findings, test results, imaging studies) and symptoms that together characterize a particular disease process. Such a diagnostic approach has been termed Syndromic Analysis (Syn Ana).

The following are the 5 steps of Syn Ana [30] :

1) Identify the primary organ system involved.

2) Determine whether the process is acute, subacute, or chronic in nature.

3) On the basis of history, physical examination, and nonspecific laboratory tests and imaging studies, compile a provisional list of the most likely diagnoses. 

4) Factor in any history of relevant diseases and/or medication that would effect the clinical presentation, physical findings, and results of laboratory tests and imaging studies.

5) Arrive at the correct diagnosis and its etiology by utilizing appropriate specific laboratory tests, cultures, imaging studies, and biopsy results  to rule out the other preliminary diagnoses.