Inferior dislocation of the patella

Intra-articular horizontal dislocation of the patella: a rare injury and review of the literature

Acute traumatic intra-articular dislocation of the patella is not a common presentation in orthopaedic practice; less frequently observed than extra-articular dislocation of the patella. In some of these cases, closed reduction is not possible and an open reduction in the operating theatre must be performed. In this case report, we present an elderly patient with an intra-articular horizontal dislocation of the patella without any other bony or ligamentous lesions seen in a postreduction MRI. We conducted a literature review looking at intra-articular patella dislocations, identifying 64 published studies (articles, case reports and papers). The following sources of data were searched until December 2017: PubMed, OVID, Google Scholar, Scopus, using the search strategy of (intra-articular dislocation of patella, horizontal patellar dislocation) with no limitation on the year or language of publication. The patient presented in this case report was managed with a closed reduction under general anaesthesia, without the need of any surgical intervention. As proposed in the literature, the hypothesis of an intra-articular entrapment of the patella due to the trapped osteophytes of the superior pole of the patella into the intercondylar notch was thought to be the cause of intra-articular dislocation in this elderly patient.

Two cases of inferior dislocation of the patella with impaction into the femoral trochlea of osteophytes on the superior pole of the patella

Traumatic dislocation of the patella is classified as lateral, medial, or intra-articular according to the direction of dislocation. Lateral dislocation is the most common type of patellar dislocation, and intra-articular dislocation is rare. Intra-articular dislocation is classified as superior, inferior, or vertical dislocation. Inferior dislocation is categorized as Type I, which occurs in young people, and Type II, which occurs in the elderly. In Type II, osteophytes on the superior pole of the patellar are believed to become entrapped in the intercondylar notch, dislocating the patella inferiorly. These were two extremely rare cases of inferior dislocation of the patella in elderly people. The mechanism involved was considered to be the exertion of sudden upward traction on the patella due to the muscular force of the quadriceps when the knee was flexed, causing osteophytes on the superior pole of the patella to become impacted into the femoral trochlea. Dislocations were successfully reduced without anesthesia, and osteophyte resection or complete osteophyte fracture during reduction meant that there was no recurrence of the dislocation.

Traumatic inter-condylar dislocation of the patella: report of two cases

Traumatic patellar dislocation usually occurs in the lateral direction. In a few cases, however, the patella rotates around its horizontal axis and becomes wedged between the femoral condyles. We report two cases of traumatic inter-condylar patellar dislocation that required surgical management.

Intra-articular dislocation of the patella

We present an unusual case of a chronic, irreducible intra-articular dislocation of the patella in an elderly nursing home resident. The patient had been unable to weight bear for 3 weeks. Radiographs in the emergency department (ED) confirmed the intra-articular dislocation with the superior pole lodged in the intercondylar notch. She underwent two failed closed reduction attempts and subsequently required an open reduction under general anaesthesia.

Recurrent locked knee caused by an impaction fracture following inferior patellar dislocation: a case report

Introduction

Locked knee caused by inferior patellar dislocation is considered rare in elderly patients. It was originally thought that, in the osteoarthritic knee, osteophytes on the pole of the patella become entrapped in the inter-condylar notch, which is managed by performing closed reduction and immobilization in a knee splint for three to four weeks. We present an unusual case of a locked knee with an impaction fracture. To the best of our knowledge, there have been no previous reports of such impaction fractures managed with arthroscopy.

Case presentation

We present an unusual case of an 88-year-old Caucasian woman with moderate arthritis who had a locked knee caused by an impaction fracture of the patella into the lateral femoral condyle. In this case report, we describe the need for arthroscopic surgery to prevent relocking of the knee in these patients.

Conclusions

This case report emphasizes the need for careful assessment of locked knees in elderly patients. Impaction fractures should be considered in all rare cases of patellar dislocation, and we advocate arthroscopic assessment of the articular cartilage in these patients. This is an important consideration, as the population demographics change and such impaction fractures may become more common in patients with degeneration in the knees.

Recurrent inferior patellar dislocation in an osteo-arthritic knee

A case of inferior dislocation of the patella in an 80-year-old woman with an osteo-arthritic knee is presented. This is a rare injury in the degenerate knee and the first case in which recurrence, the need for operative reduction and intra-articular damage has been demonstrated.