This chapter presents the key facts, clinical presentations, physical examinations, diagnostic testings, treatments, and prognosis of the knee and leg injuries such as knee dislocations, anterior cruciate ligament (ACL) injuries, posterior cruciate ligament (PCL) injuries, tibia and fibula fractures or dislocations, and lateral collateral ligament (LCL) injuries. Due to the limitations of the ED assessment, the suspected discharge diagnosis is often unconfirmed, and close follow-up is required to confirm the diagnosis, monitor symptoms and guide further management. Physical exam of the acutely injured knee in the ED is often compromised by acute pain and swelling. When an occult, non-displaced fracture is suspected, then management should include immobilization in ~30° of flexion, crutches, non-weight-bearing status, and follow-up with orthopedic surgery within a few days. Though not absolutely indicated, local practice patterns may elect to confirm the presence or absence of a fracture in the ED with computer tomography (CT).