Utility of Diagnostic Arthroscopy Before Medial Patellofemoral Ligament Reconstruction in Pediatric and Adolescent Patients Without Articular Findings on Magnetic Resonance Imaging.

Background: Medial patellofemoral ligament (MPFL) reconstruction is frequently used to manage recurrent patellar instability. Diagnostic arthroscopy is commonly performed before MPFL reconstruction to identify, confirm, and address intra-articular pathology. However, when preoperative magnetic resonance imaging (MRI) does not demonstrate intra-articular lesions, it is unclear how often diagnostic arthroscopy in pediatric patients alters surgical management. Purpose: To determine the utility of diagnostic arthroscopy in young patients undergoing MPFL reconstruction who had no intra-articular chondral or osteochondral pathology, meniscal tears, or loose bodies identified on preoperative MRI, and to characterize intra-articular pathology detected on arthroscopy but not identified on MRI. Study Design: Case series; Level of evidence, 4. Methods: This was a retrospective cohort study of patients who underwent MPFL reconstruction from 2014 to 2025. Inclusion criteria were age ≤18 years at the time of surgery, available preoperative MRI without intra-articular chondral or osteochondral pathology, meniscal tears, or loose bodies; and MPFL reconstruction with concomitant diagnostic arthroscopy. Exclusion criteria were congenital or syndromic patellar instability, prior ipsilateral knee surgery, absence of diagnostic arthroscopy, and MRI with intra-articular cartilage damage, osteochondral fractures, subchondral fractures, loose bodies, or meniscal tears. Results: A total of 626 knees were initially identified. After application of exclusion criteria, the final cohort included 81 knees. The mean age was 14.9 years, and 77% patients were female. Of the knees excluded for operative MRI findings, the most common were loose bodies, articular cartilage injuries, and osteochondral fractures. In the final cohort, 35 of 81 (43.2%) knees had arthroscopic pathology, which included chondral changes in multiple sites (n = 35; 43%), loose bodies (n = 3; 4%), and meniscal tears (n = 1; 1%). Overall, 10 of 81 (12.3%) knees underwent changes in management based on arthroscopic findings, including chondroplasty (n = 8; 10%) and loose-body removal (n = 3; 4%). Conclusion: Diagnostic arthroscopy altered management in 12.3% of pediatric MPFL reconstructions in the absence of intra-articular chondral or osteochondral pathology, meniscal tears, or loose bodies on MRI. These results suggest that routine diagnostic arthroscopy may provide clinically meaningful value only in a subset of patients by identifying pathology not appreciated on MRI.