Imaging of the Patellofemoral Joint
Imaging is paramount in the assessment of the patellofemoral (PF) joint as it provides an objective way of detecting morphological abnormalities. The anteroposterior (AP) plain radiograph is not very helpful for evaluating PF joint problems, but it is very important to assess the overall limb alignment and to identify lateral patellar dislocation or subluxation. Lateral plain radiograph is the most interesting view of the knee in PF joint analysis. It allows us to assess patellar height and trochlear dysplasia. The skyline view permits us to evaluate patellar tilt and patellar morphology. The advantage of computed tomography (CT) versus plain radiographs is that it allows the evaluation of patella in the last degrees of extension (0–30°). Axial CT cuts are useful for identifying osteochondral fractures and for visualizing the trochlear morphology. CT allows the superimposition of images and the evaluation of the TT-TG (tibial tubercle-trochlear groove) distance and the patellar tilt; additionally, CT can detect torsional deformities as external tibial torsion and femoral anteversion. In comparison with CT, MRI allows evaluating the PF joint in a similar way but with thinner cuts and without radiation for the patient. MRI has the ability of visualizing the articular surfaces and the soft tissue structures, such as the medial PF ligament (MPFL).
KeywordsPatellofemoral Joint Imaging Radiographs CT scan MRI
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