Superior Patellar Dislocation: Case Report and Comprehensive Literature Review

Introduction Superior patellar dislocation can be easily misdiagnosed, as it rarely occurs. Presentation includes a high riding patella, acute knee pain, inability to perform a straight leg raise, and a skin dimple deformity. We present the first statistical analysis of this patient population, as well as the 41st reported case of superior patella dislocation. Methods Data from our case was combined with data collected from a comprehensive literature review of published superior patellar dislocation cases. All analyses were conducted using STATA/BE 17.0, and results were interpreted at a Type I Error Rate of alpha = 0.05 level of statistical significance. Results The mean age was 55.4 (+/- 14.5) years old, with females representing over half of the sample (n=24, 58.5%). There was not a significant difference in age by sex or time period. The most commonly reported mechanism of injury was hyperextension (n=15, 36.6%) and direct trauma (n=15, 36.6%). Clinical exam finding included knee locked in extension (n=38, 92.7%), severe pain (n=28, 68.2%), and skin dimpling (n=14, 34.1%). The highest reported treatment group was closed reduction with sedation (n=11, 26.8%). Discussion There should be high clinic suspicion for superior patellar dislocation when a patient in their 5th or 6th decade of life presents with direct trauma or hyperextension of the knee, skin dimpling, and a knee locked in extension. Radiographs demonstrating the inferior pole of the patella perched on the femoral condyles, with classic clinic exam findings, are sufficient to make the diagnosis. First line treatment may include closed reduction, although spontaneous reduction may also occur. Early clinical diagnosis will lead to improved patient care, early intervention, and improved pain control.