From the Research
Patella dislocation is most likely to occur during early knee flexion with external rotation of the tibia and contraction of the quadriceps, as evidenced by biomechanical and kinematic studies 1.
Mechanisms of Patella Dislocation
The mechanisms of patella dislocation are complex and multifactorial. Key factors include:
- Non-contact injuries involving knee flexion combined with valgus stress and external rotation of the tibia
- Direct trauma to the medial aspect of the patella
- Anatomical risk factors such as patella alta, trochlear dysplasia, increased Q-angle, ligamentous laxity, and weakness of the vastus medialis obliquus muscle
Risk Factors and Outcomes
Recurrent dislocations often result from damage to the medial patellofemoral ligament (MPFL), which normally provides 50-60% of the restraint against lateral displacement. After an initial dislocation, the MPFL is torn in approximately 90% of cases, creating instability that predisposes to subsequent dislocations. Women are more susceptible to patellar dislocation due to their wider pelvis and resulting increased Q-angle.
Treatment and Prevention
Understanding the mechanisms of patella dislocation is essential for proper diagnosis, treatment planning, and prevention strategies for patients with patellar instability. Treatment options may include isolated medial patellofemoral ligament reconstruction or combined trochleoplasty and ligament reconstruction, depending on the severity of trochlear dysplasia and other factors 2, 3.
Key Considerations
- The most recent and highest quality study suggests that patella dislocation is likely to occur during early knee flexion with external rotation of the tibia and contraction of the quadriceps 1
- Anatomical risk factors and ligamentous injuries play a crucial role in the development of patellar instability
- Treatment options should be tailored to the individual patient's needs and underlying anatomy.