Jordy van Sambeeck

General introduction 15 1 Clinical presentation and physical examination Patients can present with patellofemoral instability, patellofemoral pain (often referred to as anterior knee pain) or a combination of those symptoms. It can be difficult for patients to distinguish instability from pain and consequently it can be a challenge for physicians to differentiate between those problems. Patients with patellofemoral pain often describe a continuous pain that increases with certain activities. Patients with patellofemoral instability may experience a feeling of giving way of the knee as a consequence of reflective muscle relaxation due to unexpected pain or contrary a feeling of a locked knee due to a reflective muscle activation. Patellar dislocation is not always recognizedby the patient or bystanders and canbe mistaken for a subluxation because typically (in 90% of cases) the patella relocates spontaneously. After a primary patellar dislocation patients often present with pain and the inability to bear weight on the affected knee. There is often swelling due to hemarthrosis and a limited range of motion (no full extension, maximum of 60-70° flexion) on physical examination. Provocative tests are not very informative at the acute moment, but particularly unpleasant for a patient in this setting. Patients who present on outpatient clinic without a recent acute event can be examined more extensively. Inspection can provide the physician with information on patellar height with knees in 90 degrees of flexion and on lateralization and tilt of the patella with the knee in extension. The physician should asses the bony anatomy including the leg axis and femoral and tibial rotational deformities. The Q angle can be measured in laying or standing position. A patient can be asked to perform a single leg squat to assess the neuromuscular control. Active range of motion should also be tested in open chain to examine patellar tracking. During range of motion examination of the knee, the physician should look for the J-sign. The J-sign is seen when the patella shifts abruptly laterally when exiting the trochlear groove as extension progresses and is a typical finding which indicates initial excessive lateral tracking of the patella. Patellar stability can be tested by passive movement of the patella mediolaterally in a fully extended knee and by the apprehension test (figure 5). Patients should be examined for general hyperlaxity, for example by determining the Beighton score 8 .