Unilateral calf swelling can pose a diagnostic challenge in the Emergency Department. There are several differential diagnoses for this presentation, and the management of one may be a contraindication for another. Point-of-care-ultrasound (POCUS) can be used to identify the aetiology and guide management with confidence. We present a case of an elderly patient with unilateral leg swelling in which DVT was initially suspected. However, POCUS demonstrated a ruptured Baker's cyst with associated calf haematoma. The use of POCUS by emergency physicians can avoid the consequences of unnecessary or harmful treatment and missed diagnosis of venous thromboembolic disease.