gapping on varus stress radiographs, while arthritis patients have no gapping but should show signs of joint space narrowing, subchondral cysts, osteophytes, and/or sclerotic bone changes. Arthroscopy Arthroscopy is another useful tool to diagnose and assess injuries to the posterolateral corner. Arthroscopy is useful in two ways. First, a patient undergoing arthroscopy is placed under anesthesia which allows for a complete physical examination using the specialized tests described above, which can be difficult with the patient awake. A prospective study that looked at 30 patients undergoing arthroscopy found all of them to have a positive "drive through sign" during evaluation. A drive through sign occurs when there is more than 1 cm of lateral joint opening when a varus stress is applied to the knee which allows the surgeon to easily pass the arthroscope between the lateral femoral condyle and tibia . Second, arthroscopy allows the surgeon to visualize individual structures in the posterolateral knee. The specific structures that can be evaluated are the popliteus tendon attachment on the femur, the popliteomensical fascicles, the coronary ligament of the posterior horn of the lateral meniscus, and the meniscofemoral and meniscotibial portions of the mid-third lateral capsular ligament. Examination of these structures allows injuries to be identified and will direct the placement of incisions for repair or reconstruction. Prevention As with any body part, maintaining strength and flexibility of the muscles can help to prevent injuries. Specifically in the knee, the quadriceps and hamstring muscles help to stabilize the knee, and maintaining their strength and flexibility will help prevent minor stresses from developing into major injuries. Proper footwear can also help prevent injuries. Wearing shoes that are appropriate for the activity help decrease the risk of slipping or twisting forces acting on the knee. In some circumstances, prophylactic bracing or taping may reduce the risk of injury as well. Treatment Treatment of posterolateral corner injuries varies with the location and grade of severity of the injuries. Patients with grade I and II (partial) injuries to the posterolateral corner can usually be managed conservatively. Studies have reported that patients with grade III (complete) injuries do poorly with conservative management and typically will require surgical intervention followed by rehabilitation. Nonoperative treatment Conservative treatment relies on immobilizing the knee in full extension to allow the stretched or torn ligaments to heal. It is imperative that the patient keep the knee immobilized and not bear weight