Incidence of First-Time Lateral Patellar Dislocation: A 21-Year Population-Based Study

Thomas L. Sanders, Ayoosh Pareek, Timothy E. Hewett, Michael J. Stuart, Diane L. Dahm, Aaron J. Krych

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Background: First-time lateral patellar dislocation is a common orthopaedic injury. The purposes of this study were to (1) evaluate the incidence of first-time lateral patellar dislocation in a geographically-determined population, (2) report trends over time in the incidence of dislocation, and (3) describe the rate of surgical treatment. Hypothesis: The rate of patellar dislocation is highest among adolescent patients. Study Design: Cohort study. Level of Evidence: Level 3. Methods: The study population included 609 individuals identified through a multidisciplinary geographic cohort county database who were diagnosed with first-episode lateral patellar dislocation between 1990 and 2010. The complete medical records were reviewed to confirm the diagnosis and to evaluate details of injury and treatment. Age- and sex-specific incidence rates were calculated and adjusted to the 2010 US population. Poisson regression analyses were performed to examine incidence trends by age, sex, and calendar period. Results: The overall age- and sex-adjusted annual incidence of patellar dislocation was 23.2 (95% CI, 21.2-24.9) per 100,000 person-years. The annual incidence was similar between male and female patients and highest among adolescents aged 14 to 18 years (147.7/100,000 person-years). The mean age at dislocation was 21.4 ± 9.9 years, and 331 patients (54.4%) were female. During the study period, there was a significant decline in the incidence of patellar dislocation among men aged 19 to 25 years (P = 0.002) and girls aged 14 to 18 years (P = 0.025). Eighty patients received surgical treatment during the study period, including 66 patients (10.8%) for recurrent instability and 14 patients (2.3%) for acute osteochondral injury. Conclusion: With an annual incidence of 23.2 per 100,000 person-years, lateral patellar dislocation is a frequently encountered orthopaedic injury. The incidence of dislocation among adolescent patients in this cohort is higher than previously reported. Despite a decrease in the annual incidence of dislocation in adolescent girls, the overall incidence of patellar dislocation remained relatively constant over a 21-year observation period. Clinical Relevance: This study demonstrates that the incidence of patellar dislocation in adolescents is greater than previously reported.

Original languageEnglish (US)
Pages (from-to)146-151
Number of pages6
JournalSports Health
Issue number2
StatePublished - Mar 1 2018


  • incidence
  • instability
  • patellar dislocation
  • recurrence

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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