High Rates of Abnormal Patellofemoral Morphology in Adolescents With Anterior Knee Pain: A Retrospective Review.

Background: Anterior knee pain is a common reason for referral to a pediatric orthopedic surgeon. Although previous studies have found that adults with anatomic risk factors for patellofemoral instability (patella dislocation) are predisposed to anterior knee pain, no studies have elucidated the relationship between anatomic risk factors for patellofemoral instability and anterior knee pain in children. Purpose : We sought to characterize common radiographic findings in adolescent patients with a chief complaint of anterior knee pain and to determine the prevalence of abnormal patellofemoral morphology. Methods : We conducted a retrospective review of patients 13 to 18 years old with anterior knee pain at a single tertiary care metropolitan institution from 2016 to 2021. X-rays and magnetic resonance imaging (MRI) were evaluated in those diagnosed with "chondromalacia patellae," "chondromalacia," "patellofemoral disorders," or "anterior knee pain." Patella alta, tibial tubercle-trochlear groove (TT-TG) distance, tubercle height, Wiberg patella type, patellar tilt, and trochlear dysplasia characterization were recorded. Results : Of the 293 adolescents with anterior knee pain included, 62 had bilateral anterior knee pain. Of the 172 MRIs, 72 (42%) met criteria for patella alta, Caton-Deschamps Index (CDI) >1.3, 35% had a TT-TG distance >15 mm, and 32% had lateral patellar tilt >15°. Magnetic resonance imaging findings included infrapatellar fat pad signal hyperintensity (41%) and patellofemoral dysplasia (23%). Of all 293 adolescents, 74% had images showing abnormal patellofemoral morphology, of which 30% had a history of 1 or more patellar dislocation. Overall, 40% of the adolescents had surgery, most commonly medial patellofemoral ligament (MPFL) reconstruction (18%). Conclusions : In this retrospective review, nearly 3/4 of adolescents with anterior knee pain had images showing abnormal patellofemoral morphology, including patella alta, increased TT-TG distance, trochlear dysplasia, or abnormal lateral patellar tilt; only 18% had MPFL surgery. These findings suggest that primary care providers might consider obtaining X-rays and/or MRIs to evaluate for pathology that warrants orthopedic evaluation.