Magnetic Resonance Imaging as a Stand-Alone Tool Fails to Accurately Assess Medial Patellofemoral Ligament Integrity: A Radiographic Analysis

The medial patellofemoral ligament (MPFL) is of critical importance for patellar stability and is universally incompetent in patients with patella dislocations. However, radiological (magnetic resonance imaging [MRI]) assessment of the MPFLs' integrity following dislocation is variable, adding confusion to patients and providers during treatment decision-making. We aimed to assess the reliability of MRI to evaluate MPFL integrity by measuring inter- and intraobserver agreement between a musculoskeletal radiologist and an orthopaedic surgeon, specializing in sports medicine using a novel standardized MRI-based scoring system. We anticipated higher intraobserver than interobserver reliability of MPFL integrity. We retrospectively reviewed 100 consecutive knee MRIs: 50 from patients with a clinical history of recent acute patellofemoral dislocation and 50 controls drawn from an anterior cruciate ligament (ACL) injury cohort who had no history or clinical symptoms of patellar instability. Two blinded reviewers, an orthopaedic surgeon with fellowship training in sports medicine and subspecialty expertise in patellofemoral pathology, and a fellowship-trained musculoskeletal radiologist, independently evaluated the MPFL on axial MRIs. Demographic characteristics (age, body mass index, sex) did not differ significantly between the instability and control groups. Eight percent of patellar instability patients had their MPFL graded as intact in our first review. Twenty-six percent of ACL control patients had their MPFL graded as at least attenuated. Intraobserver reliability was substantial to excellent and interobserver reliability was fair to moderate. Our findings demonstrate that MRI-based evaluation of MPFL integrity lacks the consistency and accuracy required for confident clinical decision-making and that MRI findings do not universally correlate with clinical history. These findings support a growing consensus that current imaging analyses alone are insufficient for surgical decision-making in patellofemoral instability, particularly in the assessment of the MPFL. Level of Evidence Level III.