Background/Purpose: Clinically-suspected septic
arthritis is culture-negative in 18-43% of cases.  These patients are often treated surgically
with associated morbidity, prolonged hospital stays and high medical costs.  Patients with culture-negative (CN) septic
arthritis may differ in important ways from their culture-positive (CP)
counterparts, including the possibility that such patients could be
successfully managed without surgery. The purpose of our study is to compare
the clinical characteristics and outcomes between CN and CP patients with
surgically-treated septic arthritis.

Methods: We conducted a retrospective study that
included all patients ages 18 and older admitted to a single, tertiary-care
hospital between 1998 and 2015 who were diagnosed with monoarticular
septic arthritis and were treated with antibiotics and surgery. We excluded all
cases of osteomyelitis and polyarticular or
prosthetic joint infection.

Results: Of 314 patients with clinically suspected
and surgically treated septic arthritis, 104 were CN and 210 were CP.  The groups were similar with regard to age,
gender and presence of associated comorbidities [Table 1]. Though,
significantly more CP patients had known, pre-existing joint pathology
(p=0.003). The most common joint affected was the knee, which was more
frequently involved in the CN group (p=0.03), while the shoulder was more often
involved in the CP group (p=0.01) [Figure 1]. 
The clinical presentations and outcomes differed significantly between
the two groups with more severe disease [Table 1] and less favorable outcomes
[Table 2] noted among those in the CP group. Nearly 10% of patients in the CN
group were diagnosed with another cause of inflammatory arthritis within one
year of follow-up.

Conclusion: This study suggests that patients
presenting with suspected septic arthritis have less severe disease and better
outcomes when their synovial fluid cultures are negative. Many CN patients are
diagnosed with another cause of inflammatory arthritis in follow-up.  Non-surgical treatment may be appropriate for
patients with suspected septic arthritis when synovial fluid cultures are
negative.