Editorial Commentary: Surgical Treatment Algorithm for Patellofemoral Recurrent Instability.

As a frame of reference, the patella can be "out" of the trochlea owing to extensor mechanism malalignment, such as an increased tibial tuberosity (TT)-trochlear groove (TG) distance, or the trochlea can be "out" of the patella if the TG is misplaced owing to increased internal femoral torsion. Both lead to an increased Q angle and patellofemoral maltracking. Medial patellofemoral ligament reconstruction acts as a medial checkrein against instability, but it does not solve maltracking in every case. TT medialization is recommended for an increased TT-TG distance, and TT anteromedialization additionally diminishes patellofemoral contact pressure. TT distalization can address patella alta. Trochleoplasty is a direct treatment for trochlea dysplasia. Varus osteotomy in cases of valgus deformity, and derotational femoral osteotomy in cases of increased internal femoral torsion, can realigning the trochlea with the patella. Derotational osteotomy addresses the misplaced trochlea-and not the patella or extensor mechanism. Cases of increased external tibial torsion (ETT) and foot pronation both result in compensatory increased hip internal rotation leading to knee internal rotation and lateral shear forces on the patella. In such cases, derotational supra-TT osteotomy provides better results than medialization because medialization could increase ETT and exacerbate symptoms. Supra-TT osteotomy results in TT medialization, whereas infra-TT osteotomy does not, so patients with increased ETT and an increased TT-TG distance may require supra-TT derotational osteotomy whereas those with increased ETT and a regular TT-TG distance may require infra-TT derotational osteotomy-if tibial derotational osteotomy is to be performed. Indications for medial patellofemoral ligament reconstruction, various TT transfers, trochleoplasty, varus osteotomy, and derotational osteotomy (with rotational population means and thresholds for surgical treatment) are finally presented, in addition to alert signs such as a squinting pattella, a high grade J sign, a type 2 extended Q angle described by Manilov, and the inverted proximal humerus sign.