Epidemiology and Natural History of Acute Patellar Dislocation

TLDR

The study aims to define the epidemiology of acute patellar dislocation, quantify the risk of subsequent instability episodes, and identify risk factors for recurrence. A prospective cohort of 189 patients was followed for 2–5 years, with injury mechanisms, clinical examinations, and radiographic measurements recorded to evaluate risk factors. Patients with a prior history of instability were older, more often female, and had a 6.6‑fold higher odds of recurrent episodes, with 49% experiencing instability versus 17% of first‑time dislocators.

Abstract

Background The goals of this study were to (1) define the epidemiology of acute patellar dislocation, (2) determine the risk of subsequent patellar instability episodes (subluxation and/or redislocation) during the study period, and (3) identify risk factors for subsequent instability episodes. Study Design Prospective cohort study. Methods The authors prospectively followed 189 patients for a period of 2 to 5 years. Historical data, injury mechanisms, and physical and radiographic measurements were recorded to identify potential risk factors for poor outcomes. Results Risk was highest among females 10 to 17 years old. Patients presenting with a prior history of instability were more likely to be female (P < .05) and were older than first-time dislocation patients (P < .05). Fewer first-time dislocators (17%) had episodes of instability during follow-up than patients with a previous history of instability (49%) (P < .01). After adjusting for demographics, patients with a prior history had 7 times higher odds of subsequent instability episodes during follow-up than first time dislocators (adjusted odds ratio = 6.6, P < .001). Conclusions Patellar dislocators who present with a history of patellofemoral instability are more likely to be female, are older, and have greater risk of subsequent patellar instability episodes than first-time patellar dislocators. Risk of recurrent patellar instability episodes in either knee is much higher in this group than in first-time dislocators.