Although intra-articular knee injection is not a complicated procedure, it could be difficult to assess whether the tip of the needle lies free in the joint or is embedded in synovium or other intra-articular soft tissues. The purpose of this study was to evaluate the accuracy rate of intra-articular injection using anteromedial (AM), anterolateral (AL), lateral midpatellar (LMP), and medial midpatellar (MMP) portals in cadavers. In this study 156 knees of 78 fresh cadavers were included. Anterolateral and AM injection to both knees of 39 cadavers (78 knees) were performed. MMP and LMP injection to both knees of other 39 cadavers were also performed. Accuracy rate was the highest (85%) in the AL injection portal and lowest in the MMP portal (56%). In conclusion, the accuracy obtained with use of the MMP portal was significantly lower than that obtained with the use of either the AM (P < 0.05), AL (P < 0.0001), or LMP (P < 0.05) portal. Although AL injection site resulted in good intra-articular delivery with 85% accuracy rate and with a lower incidence of soft tissue infiltration, the results were not statistically significant when compared to AM and LMP portals. Therefore, any of these three portals might be preferred depending on the experience of the physician. On the other hand, 100% accuracy could not be obtained through any portals in the study, which should be kept in mind when treating knee problems with intra-articular medications.