Purpose or Case Report: Depending on the age of the patient, knee MRI may be a daunting exam. Physicians may have a higher threshold to order MRI in the pediatric setting compared to the adult setting. Few if any studies are available which attempt to predict the prevalence of MRI findings based on the patient’s presenting history in the sports medicine setting. Our objective was to determine the prevalence of knee pathology using MRI in two groups of pediatric patients: those with an acute event, and those with knee pain without history of acute event.
Methods & Materials: A database of patients who were seen at a tertiary care center non-surgical sports medicine was accessed. This study included those who presented with knee pain, had a knee MRI, and had been categorized by a sports medicine physician into acute or nonacute/overuse groups. A consensus read between a fellowship-trained musculoskeletal radiologist and a pediatric radiology fellow was performed for each MRI using a structured reporting system. Follow-up MRIs on the same knee were excluded.
Results: A total of 26 knee MRIs performed on patients with acute pain (average age 14.7y, range 11-26y) and 26 MRIs in those with nonacute pain (average age 12.8y, range 7-17y) were reviewed. Significantly more knees with imaging findings of patellofemoral instability were seen in the acute group (50%) versus nonacute group (15%), p<0.05. The acute group included more bone contusions (58% vs 4%, p<0.0001) and soft tissue edema (27% vs 0%, p<0.01). More Baker’s cysts were seen in the nonacute group (27% vs 4% in acute), p<0.05. Prevalence of extensor mechanism abnormalities such as patellar and quadriceps tendinopathy and Osgood-Schlatter disease was 15% in the acute and 27% in the nonacute groups. Prevalence of MCL injury in the acute vs nonacute groups was 11% vs 0%, cartilage injury was 35% vs 11%, and osteochondritis dessicans was 0% vs 11%. Prevalence of cruciate ligament injury, meniscal injury, and lateral collateral ligament complex injury was low in both groups (<4%).
Conclusions: In the sports medicine setting, patients with acute injury are more likely to have patellofemoral instability, bone contusions, and soft tissue edema than those with a nonacute presentation. Patients with a nonacute presentation are more likely to have Baker’s cysts. The prevalence of ligamentous and meniscal injury was low in this nonsurgical setting.