Diagnosis of patellofemoral malalignment by computed tomography

Conventional radiographic assessment of the patellofemoral joint (PFJ) is often unsatisfactory for a variety of technical and theoretical reasons. Using a simple device designed to allow easy and reproducible control of knee flexion, we used computed tomography (CT) to evaluate the PFJ in 10 normal volunteers and five patients with a history suggestive of recurrent subluxation or dislocation of the PFJ. At full extension of the knee the patients with a history of malalignment showed an abnormal patellar centralization and tilt compared with those of the normal volunteers. The abnormalities were absent or less pronounced on images obtained at 20 and 45 degrees of knee flexion.