Forty-six knees in 41 patients that had undergone high tibial osteotomy (HTO) were evaluated to assess the potential correlation between alteration in the inclination of the proximal tibial articular surface and subsequent patellar height. Of the knees examined, 61% lost > or =5 degrees of posterior tibial inclination after HTO, whereas 54% of knees showed a relative lowering of patellar height of >10%, as measured by the Insall-Salvati ratio. The loss of the normal posterior tibial inclination was found to have a statistically significant association with the subsequent loss of the patellar height. Clinically, these results suggest that careful preservation of the posterior tibial inclination at the time of HTO could minimize the risk of subsequent patellar infera and alteration in patellofemoral mechanics.