...14 cases (10.7%) of medial meniscus injuries, nine cases (6.9%) of lateral meniscus injuries and 11 cases (8.4%) of arthritis were found in the control group. ...Spearman's two-tailed test showed that there were significant positive correlations between the patient age and the medial meniscus injury, lateral meniscus injury, anterior cruciate ligament injury, posterior cruciate ligament injury, effusion, and arthritis, respectively. Compared with the control group, the patellar instability enhanced the correlations between the tissue injuries and the older age in the patient group. ...in the patient group, more severe trochlear dysplasia and patella alta would result in younger onset age of patellar instability. ...this clinical observation showed that more severe trochlear dysplasia and patella alta were often accompanied by the younger onset age of patellar instability among these patients.