PATELLAR DISLOCATION AND PATELLAR INSTABILITY PANORAMIC REVIEW

Abstract

Introduction: Primary patellar dislocation is usually the initial manifestation of patellofemoral instability. Among the long-term repercussions of this disorder are recurrent dislocation and indefinable knee dysfunction. At present, there is no agreement on the optimal treatment of patellar dislocation.

Objective: to detail the current information related to patellar dislocation, epidemiology, mechanism of action, clinical evaluation, imaging evaluation, classification, differential diagnosis, treatment and complications of the disease.

Methodology: a total of 30 articles were analyzed in this review, including review and original articles, as well as clinical cases, of which 22 bibliographies were used because the other articles were not relevant to this study. The sources of information were PubMed, Google Scholar and Cochrane; the terms used to search for information in Spanish, Portuguese and English were: patella, knee anatomy, patellar dislocation, knee instability.

Results: Approximately 5% of the time it is related to osteochondral fractures. To define whether a patella is high or low, a lateral radiograph should be taken with the knee in 30° of flexion to determine Blumensaat's line. The increase in the Q angle facilitates patellar dislocation. Most patellar dislocations are related to congenital anomalies of the patella or trochlea, high patella, hypoplasia of the vastus medialis and hypertrophy of the lateral retinaculum.

Conclusions: Patellar dislocation is usual in individuals with connective tissue disorders and hypermobility, the patella can be dislocated laterally, superiorly or intra-articularly, presenting different mechanisms of action for each case. It is important to have a good knowledge of the anatomy and to measure the Q angle because the increase of this angle facilitates patellar dislocation. It is essential to establish the etiology of the dislocation, especially in those with recurrent dislocations as this may alter the management plan. In addition to the clinical evaluation it is important to request anteroposterior, lateral knee and axial projections. When conservative treatment is chosen, reduction and immobilization with a cast or orthosis should be performed with the knee in extension, the long knee brace can be used, with or without arthrocentesis to relieve the symptomatology; surgical treatment is mostly used in recurrent dislocations. At the moment, no surgical technique is able to correct all the problems of patellar alignment. It should be kept in mind that the surgical procedure should take into account the individual's age, diagnosis, activity level and the situation of the patellofemoral joint. Patellofemoral instability should be treated with the goal of correcting all of the alignment issues. The usual complications are loss of knee mobility, recurrent dislocation and patellofemoral pain.