Minimal Invasive Medial Patellofemoral Ligament Reconstruction by Hamstring Tendon Auto-graft

Anatomic abnormalities can lead to patellar instability. Valgus alignment at the knee leads to an increased Q angle and increased lateral tension on the patella. Similarly, rotational misalignment of the extremity specifically, increased femoral anteversion combined with external tibial torsion leads to increased lateral tension on the patella.

With increased flexion at the knee, the bony constraints become more important and trochlear dysplasia can lead to insufficient constraint in flexion. Patients with patella alta engage their bony constraints at a deeper flexion angle and can therefore be more prone to subluxation and dislocation.

In extension the important static constraint to lateral subluxation and dislocation is the medial patellofemoral ligament (MPFL). In this same range, the vastus medialis obliqus acts as a dynamic restraint to instability. In any single patient, several of these factors can act together, leading to his or her symptoms.

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