Histological findings of avulsion tear-type medial patellofemoral ligament injury in acute patellar dislocation

Acute patellar dislocation is a common injury that occurs during a variety of activities and accounts for 2–3% of knee injuries.1 Since 1990, especially over the past 5 years, more attention has focused on the medial patellofemoral ligament (MPFL) of the medial retinacular components. In several biomechanical studies, the MPFL has proved to be the primary restraint to lateral translation of the patella among the medial patellar stabilisers, and many clinical findings have shown that acute patellar dislocation is associated with MPFL injuries at a high rate.2–9 In 1999, Nomura6 classified MPFL injury in acute patellar dislocation into two types, avulsion tear and substantial tear. An avulsion tear is a detachment-type injury limited to the undersurface of the MPFL at the femoral attachment. It was suspected that this injury may result from a specific structure of the MPFL at the femoral attachment. This study was to evaluate the histological findings of the avulsion tear-type injury of the MPFL in acute patellar dislocation. A 23-year-old woman sustained initial dislocation of the left knee while climbing a step (case 1). Five days after the injury, we …