Patella dislocations are a moderately common injury. Sometimes they are a one-off event. Other times they can lead to recurrent dislocations and pain. In our study1, we found that recurrence was common, occurring in over 70% of individuals. Therefore, anyone who suffers a dislocation must have adequate treatment and rehabilitation for the first dislocation. Treatment should comprise regaining early movement of the knee, then an extensive quadriceps muscle strengthening program.
Having a way of predicting who is at risk of further dislocations would be helpful. Our study found that the risk factors for recurrent dislocation were being female and young (under 15 years). We also found a higher chance of recurrence if the person’s other patella had dislocated and if the mechanism of injury was deemed “moderate” rather than “severe” in intensity. Finally, we postulated that recurrence was higher in individuals with anatomic or biomechanical abnormalities of the patellofemoral joint.
A recent study expanded on ours2. This study showed that risk factors were:
1. being young.
2. have open growth plates (meaning the person was still growing).
3. a condition called trochlear dysplasia (having an abnormality of the groove the patella slides in).
4. patella alta (the kneecap sits higher than usual).
5. having an increased TTTG (meaning the attachment of the patellar tendon is more to the side than usual).
If someone who suffered a dislocation had none of the above risk factors, the chance of recurrence was 10%. However, if the individual had two risk factors, the recurrence rate leapt to 50%; and for three risk factors was 80%.
So first-time dislocators not only need appropriate management of their dislocation, but they need an accurate assessment of risk factors to determine the risk of further episodes.
- Richardson R, Brown GC: Acute Patellofemoral Dislocation: the Natural History. Australian Orthopaedic Association 59th Annual Scientific Meeting. Brisbane 10-15 October 1999
- Devitt, B: Presented at the Australian Knee Society. Canberra October 2019