This study developed the Recurrent Instability of the Patella (RIP) Score to predict long-term recurrence risk after a first-time lateral patellar dislocation. Using a population database of 500,000+ patients, 81 patients were followed for a mean of 10.1 years. The score uses four variables — age, skeletal maturity, trochlear dysplasia, and TT-TG/patellar length ratio — to place patients into low, intermediate, or high-risk categories.
When a young patient walks in after a first patellar dislocation, the reflex is to reassure them and start physical therapy. But nearly half will dislocate again, and the highest-risk patients have a nearly 80% chance of recurrence over 10 years.
The RIP Score gives you a decision framework at that first visit. Add up the points: age under 25 (2 pts), open physes (1 pt), any Dejour dysplasia (1 pt), TT-TG/PL ≥0.5 (1 pt). A score of 4-5 should prompt a serious conversation about early surgical stabilization before the next dislocation damages more cartilage.
Prior scoring systems excluded operatively managed patients — meaning they were calibrated on a self-selected low-risk group and were not generalizable to the patients who actually need risk stratification most. The RIP Score corrects this by using competing risk regression that includes surgical cases.
The TT-TG/patellar length ratio is the key radiographic variable: normalizing TT-TG to patellar length accounts for patient size and outperforms absolute TT-TG distance alone, with an odds ratio of 6.1 for recurrence when the ratio is ≥0.5.
This study developed the Recurrent Instability of the Patella (RIP) Score to predict long-term recurrence risk after a first-time lateral patellar dislocation. Using a population database of 500,000+ patients, 81 patients were followed for a mean of 10.1 years. The score uses four variables — age, skeletal maturity, trochlear dysplasia, and TT-TG/patellar length ratio — to place patients into low, intermediate, or high-risk categories.
When a young patient walks in after a first patellar dislocation, the reflex is to reassure them and start physical therapy. But nearly half will dislocate again, and the highest-risk patients have a nearly 80% chance of recurrence over 10 years.
The RIP Score gives you a decision framework at that first visit. Add up the points: age under 25 (2 pts), open physes (1 pt), any Dejour dysplasia (1 pt), TT-TG/PL ≥0.5 (1 pt). A score of 4-5 should prompt a serious conversation about early surgical stabilization before the next dislocation damages more cartilage.
Prior scoring systems excluded operatively managed patients — meaning they were calibrated on a self-selected low-risk group and were not generalizable to the patients who actually need risk stratification most. The RIP Score corrects this by using competing risk regression that includes surgical cases.
The TT-TG/patellar length ratio is the key radiographic variable: normalizing TT-TG to patellar length accounts for patient size and outperforms absolute TT-TG distance alone, with an odds ratio of 6.1 for recurrence when the ratio is ≥0.5.