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traumatizing the tendon’s insertion on the tibial tubercle during the child’s growth spurt The patients have localized tenderness and occasional swelling over the tibial tubercle The patient will refuse to extend the knee against force (e.g., perform a deep knee bend) and have difficulty going up or down stairs, although they may have a normal gait on a level surface To eliminate the possibility of a neoplasm or a secondary avulsion if there is an acute change, the physician should obtain radiographs In Osgood–Schlatter disease, the radiographs will be normal or show irregularity of the tubercle Patellofemoral dysfunction (PFD) or patellofemoral pain syndrome may be caused by misalignment of the extensor mechanism of the knee The vastus lateralis, vastus intermedius, and rectus femoris pull the patella slightly laterally and need to be balanced perfectly by the vastus medialis to keep the patella tracking across the articular cartilage correctly The patient with PFD may have patellar pain with running and especially while going down inclines or stairs The patient may also have the sensation of the knee giving out when descending, although an actual fall does not usually occur The patient may describe pain when sitting for a prolonged time with the knee flexed at 90 degrees (e.g., in class) The pain disappears once the patient is ambulatory On examination, the patient may have a medially displaced patella, tenderness of the articular surface of the patella, and a positive patellar stress test This test is performed with the patient in the supine position with the knee fully extended The patient is asked to relax the quadriceps so that the physician can move the patella With the patella pulled inferiorly, the physician should gently press down on it and ask the patient to tighten the quadriceps The patient should be asked to “push the knee into the examination table.” This will move the patella superiorly as the physician continues to press down A patient with PFD will have acute pain with this maneuver Radiographs are normal Patellar tendonitis, or “jumper’s knee,” occurs in patients during their growth spurt, especially those involved in jumping (knee extension) sports The knee is tender on the inferior pole of the patella and the adjacent patellar tendon, but not on the tibial tubercle; radiographs are generally normal Prepatellar bursitis occurs after acute or chronic trauma to this bursa, which overlies the patella The patient will have swelling over the anterior aspect of the knee, especially over the patella A septic bursitis may need to be ruled out by needle aspiration Osteochondritis dissecans (OCD) is the separation of a small portion of the femoral condyle with the overlying cartilage The patient is usually an adolescent with a 1- to 4-week history of nonspecific knee pain The physical examination may be normal, or the femoral condyle may be tender with the knee flexed Because AP and lateral radiographs may not show the lesion, a tunnel or intercondylar view should be obtained Iliotibial (IT) band syndrome usually occurs in older runners who complain of pain over the lateral femoral condyle The repetitive movement of the IT band across the lateral femoral condyle as the knee flexes and extends causes this pain When examined, the patient is tender over the lateral femoral epicondyle, palpable cm above the joint line Radiographs are normal The Baker cyst is a herniation of the synovium of the knee joint or a separate synovial cyst located in the popliteal fossa The patient complains of popliteal pain and swelling only if the cyst enlarges The sac may be palpated in the posterior medial aspect of the popliteal space For the most part, radiographs will be normal or show soft tissue swelling Ultrasound may be needed to diagnosis Baker cyst In any patient with knee pain, with or without a history of trauma, the following must be considered: benign (e.g., osteochondroma and nonossifying fibroma) and malignant tumors (e.g., osteosarcoma or Ewing sarcoma), the various causes of monoarticular arthritis (see Chapter 60 Pain: Joints ) and hip disease that may present with knee pain (e.g., slipped capital femoral epiphysis or Legg–Calvé–Perthes disease, an idiopathic avascular necrosis of the proximal femoral epiphysis) EVALUATION AND DECISION Four points are critical in the patient’s history: (i) the activity and forces that led to the injury (e.g., direction of the force, whether the foot was fixed); (ii) the initial location of the pain; (iii) any sensations or noises (e.g., “locking,” “pops,” or “tears”); and (iv) the timing of any swelling Most severe injuries (e.g., ACL, collateral ligament, or meniscal injuries) occur with high-velocity weight-bearing activities, especially running and pivoting, or direct valgus or varus stress Direct trauma to the front of the knee may cause posterior cruciate ligament injuries or patellar fractures, whereas lateral or medial forces may cause collateral or cruciate ligament damage or fractures Although the knee may “hurt all over” when seen in the ED, the patient may be able to localize the initial pain Meniscal or collateral ligament injuries cause pain on the lateral or medial aspect of the knee, whereas ACL injuries hurt just inferior to the patella, and Osgood–Schlatter disease is painful over the tibial tubercle Distinct popping noises or tearing sensations are reported in ACL injuries and patellar dislocation Locking of the knee may be reported in meniscal injuries but usually not immediately after the injury The sensation of the knee “giving out” may occur with meniscal injuries or PFD Swelling after acute injury should raise concern for significant pathology Swelling within hours strongly suggests hemarthrosis from an ACL injury, meniscal injury, or osteochondral fracture, while swelling with other knee fractures is commonly seen later The possibility of abuse in young children must always be considered, especially if the injury is unexplained, the history is implausible, or the delay in seeking medical care was unreasonable In subacute injuries, ask about hip or groin pain because the hip and knee share sensory nerves Legg–Calvé–Perthes disease or a slipped capital femoral epiphysis may cause anterior thigh or knee pain Patellar pain and the sensation of the knee giving way without actually falling when going down stairs or inclines suggest PFD Examination of the patient should include walking and standing, if possible, to check for medially deviated “squinting” patellae Inspect and palpate the knee in two positions, sitting relaxed with the knees at 90 degrees and supine When sitting, inspect the knees for swelling and tenderness (e.g., swelling and tenderness over the tibial tubercle in Osgood–Schlatter disease, or joint line tenderness in meniscal injuries) With the patient supine, repeat inspection and palpation over the joint line, collateral ligaments, patella, proximal fibula, tibial tuberosity, and popliteal space If the knee appears swollen, check for an effusion by milking any joint fluid centrally toward the patella Normally, synovial fluid coats the patellar surface but does not separate the patella and femur When fluid separates the two bones, a sharp pat on the patella results in the sensation of a tap as the two bones meet If the joint contains a large amount of fluid, the patella will not touch the femur but will feel as if it is sitting on a cushion Assess both active and passive ROM of the knee The physician should test for collateral and cruciate ligament damage, meniscal injuries, patellar subluxation, and PFD, using the appropriate maneuvers ( Table 42.2 ) although most maneuvers have poor diagnostic accuracy when used in isolation after an acute injury TABLE 42.2 SUMMARY OF DIAGNOSTIC MANEUVERS FOR THE INJURED KNEE Maneuver Diagnosis Collateral laxity test (Fig 42.4 ) Lachman test (Fig 42.3 ) Posterior drawer test (Fig 42.5 ) McMurray test (Fig 42.6 ) Apley compression test (Fig 42.7 ) Patellar apprehension test Patellar stress test Collateral ligament injury Anterior cruciate ligament injury Posterior cruciate ligament injury Meniscal injury Meniscal injury Patellar subluxation Patellofemoral pain syndrome A neurovascular examination should include palpation of the posterior tibial and dorsalis pedis pulses and testing of the peroneal nerve function The deep peroneal nerve innervates the ankle dorsiflexors and the extensor hallucis longus, which can be tested by opposing dorsiflexion of the great toe It also supplies sensation to the web space between the great and second toes Patients with knee symptoms should have a careful hip examination because patients with avascular necrosis of the femoral head or a slipped capital femoral epiphysis may present with anterior thigh or knee pain All patients with acute knee injuries should have AP and lateral radiographs, and if indicated, a patellar (or skyline view) radiograph The Ottawa Knee Rules have demonstrated 100% sensitivity for knee fractures in large, prospective, multicentered adult trials Studies in children are limited but they also demonstrated a sensitivity of 100% (95% confidence interval = 95% to 100%) in a study involving 750 children of whom 70 had fractures According to these rules, radiographs are required of children only if the patient has any of the following findings: (i) isolated tenderness of the patella, (ii) tenderness of the