Posttraumatic knee pain is a common presentation in the emergency department (ED). The use of clinical decision rules can rule out reliably fractures of the knee and reduce the unnecessary cost and radiation exposure associated with plain radiographs. If ligamentous or meniscal injury to the knee is suspected, the ED physician should arrange for expedited follow- up with the patient's primary care physician or an orthopedic specialist for consideration of an MRI and further management. Patients presenting after high-energy mechanisms are at risk for occult fracture and vascular injuries. ED providers must consider these injuries in the proper clinical setting.