Dynamic arthroscopy in retropatellar cartilage defect: identifying trochlear ridge impingement and guiding towards mini-trochleoplasty.

Retropatellar (RP) chondral defects are commonly associated with trauma, sports-related injuries, or patellar dislocations. Effective management typically requires both cartilage repair and correction of underlying predisposing biomechanical factors. However, conventional imaging modalities may fail to detect subtle abnormalities.We describe a young female with persistent anterior knee pain in the absence of trauma or instability. Imaging studies, including radiographs and magnetic resonance imaging (MRI), confirmed an RP chondral defect, with no evidence of patella alta, malalignment or significant trochlear dysplasia. Surgical management was initiated with the focus on cartilage repair by autologous chondrocyte implantation (ACI). During first-stage arthroscopy, performed for autologous cartilage harvesting, dynamic assessment revealed a trochlear ridge impinging on the defect. This finding was considered a causative and perpetuating factor. ACI was therefore combined with mini-trochleoplasty to correct the impingement.This case demonstrates the diagnostic value of arthroscopy in detecting subtle biomechanical abnormalities. Surgeons should consider diagnostic arthroscopy as a dynamic tool to identify mechanical factors that may compromise cartilage repair outcomes.