Objectives: Few studies have investigated how to best select a donor patella for ideal surface matching when performing a patellar osteochondral allograft (OCA) transplantation. Prior studies have suggested that certain anatomic factors, such as degree of donor patellar dysplasia may play a role. Patella OCA sizing is currently based on tibial width, but other anatomic factors may improve OCA topography matching. The purpose was to investigate how donor and recipient anatomical variables influence patella OCA topography mismatch and articular step-off. Methods: In silico point-cloud models were generated from CT images of 16 patella specimens. Virtual donor allografts were implanted (diameter of 18.0 mm or 22.5 mm) in virtual defects on medial, central, and lateral articular surfaces (Figure 1). Topographical mismatch and step-off were calculated. Linear regression analysis was used to identify anatomic variables influencing these factors. Results: Overall, surface incongruity was largely unaffected by anatomic variables. For 22.5mm medial defects, medial facet length, cartilage width, and medial facet percent were significantly associated with step-off (p < 0.05). For lateral defects (both 22.5 mm and 18.0 mm), lateral facet length, cartilage width, and lateral facet percent had greater effects on articular step-off than tibial width. For 18.0mm medial defects and central defects, tibial width demonstrated a small effect on step-off (Table 1). Cartilage width and tibial width, as well as lateral length and lateral percent were significantly correlated with each other (p = 0.019) (Figure 2). Conclusions: For noncentral defects, articular step-off was strongly influenced by differences in medial or lateral facet length and percent and cartilage width. Tibial width, the current standard for allograft matching, only modestly influenced step-off for central, 18.0 mm medial, and 22.5mm lateral lesions. Since tibial width highly correlated with cartilage width, using cartilage width as a surrogate for tibial width may improve patellar osteochondral surface topography matching as it is a strong predictor of articular step off for non-central lesions. Medial and lateral facet length should also be considered for topography matching of lateral lesions and 22.5 mm medial lesions as they were the strongest overall correlates with articular step-off.