Modern management of patellar instability

Abstract

Recurrent patellofemoral instability is a disabling condition, attributed to a variety of anatomical aetiologies. Trochlear dysplasia, patella alta, an increased tibial tubercle trochlear groove distance of greater than 20 mm and soft tissue abnormalities such as a torn medial patellofemoral ligament and inadequate vastus medialis obliquus are all factors to be considered. Management of this condition remains difficult and controversial and knowledge of the functional anatomy and biomechanics of the patellofemoral joint, a detailed history and clinical examination, and an accurate patient assessment are all imperative to formulate an appropriate management plan. Surgical treatment is based on the underlying anatomical pathology with an aim to restore normal patellofemoral kinematics. We summarise aspects of assessment, treatment and outcome of patellofemoral instability and propose an algorithm of treatment.

Figures

Fig. 1

Lateral radiograph demonstrating a positive “crossing sign”. The base of the trochlear (arrow) crosses the line of the lateral femoral condyle

Fig. 2

CT arthrogram demonstrating trochlear dysplasia

Fig. 3

Axial CT scan of bilateral patellar lateral tilt

Fig. 4

Algorithm for managing patellar instability