Acute knee injuries are common presentations that frequently occur during sporting activities and can result in permanent disability. However, they often result in a single visit, seldom receive surgical intervention and, in the main, are cared for entirely by General Practitioners or Emergency Department physicians. Thorough clinical assessment and appropriate early treatment at the primary presentation is vital in order to offer the best chance of maximal functional recovery and to minimize long-term disability. This requires a sound knowledge of basic knee anatomy, careful assessment of the mechanism of injury, detection and consideration of physical ndings and the results of adjunctive investigations. This article aims to give a comprehensive review of the examination, investigation and early treatment of acute knee injuries at the primary presentation. In addition, comments on important epidemiological and aetiological factors and a brief description of basic knee anatomy are also provided.