Paediatric patellar instability encompasses many anatomic entities located along a continuum of knee extensor mechanism abnormalities. Major or minor clinical manifestations may occur at a variable age. In major forms with irreducible patellar dislocation or habitual patellar dislocation during knee flexion, shortness of the quadriceps is a consistent feature. A comprehensive aetiological work-up is in order, as syndromic conditions are common. Early surgical treatment is mandatory and should be performed by an experienced paediatric orthopaedic surgeon, as the procedure is technically challenging. Minor forms are more common; they are characterised by patellar dislocation or subluxation near terminal knee extension. The diagnosis may be difficult, particularly at the acute phase. Surgery is needed in patients with recurrent dislocation or functional impairments. The semiology of patellar instability has undergone considerable development in recent years, and a three-dimensional evaluation of patellar position can now be obtained using magnetic resonance imaging. Individually tailored surgical treatment "à la carte" remains a valid approach in 2013. However, new techniques for medial patello-femoral ligament reconstruction have modified the management strategies for adults and superseded many stabilisation procedures. Adapting these new techniques to paediatric patients and developing new procedures constitute major challenges.
Keywords: Children; Classification; Medial patello-femoral ligament; Paediatric patient; Patellar instability.
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