Differentiating Normal Healing From Infection in Total Joint Arthroplasty: An Educational and Diagnostic Tool for Emergency Providers Evaluating the Postoperative Patient.

Patients frequently present to the emergency department (ED) with pain, swelling, or erythema in the early period following total joint arthroplasty (TJA). Differentiating normal postoperative inflammation from superficial surgical site infection (S-SSI) or early periprosthetic joint infection (PJI) can be difficult due to overlapping clinical and laboratory features, particularly within the first 30 days after surgery. We seek to provide emergency providers with an efficient and evidence-based framework for differentiating normal healing from early infection following TJA. We accomplish this by reviewing postoperative physiology, temporal response of inflammatory markers and synovial fluid analysis, and existing diagnostic criteria for infection. Normal healing after TJA produces predictable inflammatory responses that commonly exceed thresholds established for chronic PJI diagnosis. Therefore, early PJI diagnosis should utilize a time-dependent interpretation of synovial fluid, while S-SSIs remain primarily clinical diagnoses. A structured diagnostic algorithm can safely reduce unnecessary testing and costs, protect against medicolegal pressures, and provide evidence-based practices for effectively detecting early infection following TJA. This is crucial in the setting of the new Transforming Episode Accountability Model (TEAM) that bundles TJA payment.