Knee injuries are among the most prevalent of bone and joint injuries, with the National Orthopaedic Society reporting in June 2001 that more than 1.08 million visits to orthopaedic surgeons are made each year due to knee problems. In order to perform a good evaluation, one should first understand the anatomy of the knee joint. The knee joint is one of the largest and most complex joints in the body, consisting of the femur, tibia and patella. Cartilage covers it effectively preventing mutual grinding. The medial collateral ligament and the lateral collateral ligament protect the knee from inversion and valgus respectively, while the anterior and posterior cruciate ligaments provide stability in the anterior and posterior directions. The quadriceps tendon is the portion of the anterior thigh muscle that extends to the surface of the patella and acts as a knee extensor. Since taking a history gives you the most important information you can obtain, such as “What were you doing at the time of the injury?” questions, taking a history should be the first step in performing a knee injury. Swelling, pain, loss of function, tearing sounds, and passive flexion are often the main symptoms of a knee injury. The rate of swelling will indicate the severity of your injury, for example, if the knee swells 2-12 hours after the injury, this is most likely to be an accumulation of blood in the joint, or very likely to be an ACL injury, a meniscal injury or both. If the joint capsule is torn, there will be no significant swelling because the blood will flow into the surrounding tissues. This is why you should look carefully for swelling in the thighs and calves during your evaluation. If the patient can indicate which area is most uncomfortable, this can help you to localize the injury. However, since pain only provides some reference to the degree of injury, it is not always reliable. Sometimes a first-degree or mild injury may be more painful than a third-degree or severe injury because in a mild injury the ligaments are still attached and there is tension in the injured fibers. In complete tears and third-degree injuries, the fibrous tissue is torn apart so that the pain-producing tension is reduced. If the patient has to stop what they are doing at the same time as the injury, this often indicates a more serious injury. Eighty percent of people with ACL tears will be unable to continue their activities. Data reports on the frequency of tearing sounds heard in severe injuries vary, but in general 40-60% of ACL injuries can be heard along with the injury. In addition to ACL injuries, patellar dislocations, meniscal tears, and osteochondral fractures can also be heard. 90% of patients with ACL injuries report passive downward flexion of the knee at the time of injury, and if the patient feels a loss of control of the joint at the same time as the injury, it is often a serious condition. Physical examination is very important in the diagnosis of knee injuries, and the earlier the knee is examined after the injury, the better the prognosis. The most accurate time to examine the knee is 2-6 hours after the injury, before swelling and tension protection of the muscles develop. First, observe the limb to determine if the patient has the ability to place the injured lower extremity on the examination table. If the patient requires manual assistance to place the leg on the examination table, then a quadriceps tendon rupture should be considered. Then observe for swelling, ecchymosis, and obvious deformities. Take a pulse, especially for injuries to the end of the limb (measure the dorsalis pedis and posterior tibial artery). If problems exist they should be compared to the contralateral end. Areas to focus on for palpation include the patella, extensor system, patellar ligament, medial and lateral coalition, medial and lateral collateral ligaments, and medial and lateral tibial plateau. It is also important to palpate the knee joint to estimate the amount and extent of swollen fluid. Palpation begins at the top of the knee joint and you can squeeze the knee down to estimate the true amount of fluid present. Testing for stability is the most important part of the exam, yet it is the part of the exam that makes it the most difficult for the clinician. I strongly recommend that you perform a knee exam whenever you get the chance, whether it is a normal or injured knee. The more knees you examine, the more familiar you will feel with these methods, and the more accurate your assessment will be. Common examinations include the lachman’s test, which is designed to evaluate the anterior cruciate ligament. The lateral stress test is used to determine the continuity of the medial collateral ligament and the medial stress test is used to determine the continuity of the lateral collateral ligament. A patellar apprehension test can also be performed to examine patellar stability, especially in cases of patellar dislocation and subluxation. On imaging, fractures are present in only 6% of patients with knee trauma, and most patients with knee trauma show normal radiographs. Overall, patients 50 years of age or older with falls and trauma require x-rays. Common fractures of the knee include the patella, femoral condyle, and tibial plateau. If these fractures are present, they must be treated with attention. The Pittsburgh decision rules have a sensitivity rate of 99% and a specificity rate of 60% for the diagnosis of knee fractures. The Ottawa knee rules are 97% and 27% respectively. With regard to treatment, if you have a patient with a knee injury that requires immobilization, weight reduction, compression, cold compresses and elevation of the affected limb, you need to treat the patient after an orthopedic evaluation has been made to prevent errors. Knee immobilization braces are commonly used for acute care and can also be immobilized with filler-cast compression dressings, plaster, fiberglass, and medial and lateral splints. Most patients with acute injuries with significant exudate need to be observed for 7 days after the injury. In conclusion, knee injuries are common injuries and knowledge of the anatomy of the knee, questions to ask when collecting a history, appropriate physical examination procedures and timely findings on physical examination will greatly assist in the evaluation of the patient with a knee injury. Remember that only a complete knee dislocation is a true knee emergency, especially when combined with neurovascular injury. Be alert to the possibility of a knee fracture when there is a traumatic injury. Remember to apply RICE (Rest, Immobilization, Compression, Elevation of the Affected Extremity) – your preferred knee injury treatment principle.