Abstract
OBJECTIVE: Sympathetic joint effusion (SJE) and sympathetic synovial effusion (SSE) are recognized as causes of noninflammatory effusion with <2000 white blood cell (WBC) WBC/mm(3) in the joint and bursa, respectively. Data on normal range SJE/SSE with <200 WBC/mm(3) are unknown. We aimed to investigate the incidence, disease characteristics, and associated triggers of normal range SJE/SSE and to propose diagnostic criteria. METHODS: This retrospective study included patients hospitalized at Temple University Hospital who underwent a diagnostic arthrocentesis for joint or bursal effusion of unclear etiology from 31 January 2010 to 10 December 2016. A cohort of 72 patients with normal range synovial fluid (<200 WBC/mm(3)) fulfilled all inclusion criteria for detailed chart review. RESULTS: Annualized incidence of SJE/SSE was 1.2%. All 72 patients presented with joint pain and swelling. Twenty-three (32%) also had warmth and 12 (17%) had erythema. Symptom onset was hours to within 6 days in 45 (63%) patients. The most commonly affected joint was the knee (61, 85%). Concurrent pathology in close anatomical proximity to SJE/SSE in the same limb was documented in 29 (40%) patients, most of which (26 of 29, 89%) were infection, deep venous thrombosis, intramuscular fluid collection, and trauma. Less common pathology included adjacent recent hip surgery, loosening of hip prosthesis, and extracorporeal membrane oxygenation catheters. CONCLUSION: SJE/SSE is not uncommon in hospitalized patients and mimics both inflammatory and septic arthritis. It is seen with normal and noninflammatory synovial fluid. A search for a root cause in the same limb is warranted when evaluating acute or subacute painful joint effusions with normal range synovial fluid WBC count.