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