Background <p>Patellar measurements have been shown to provide an accurate estimate of sex. However, the influence of patellar siding on sex estimation accuracy has not been adequately explored; thus, it is less understood. This study evaluated side differences in patellar measurements and their implications on the level of sex estimation accuracy. This study sampled 104 paired patellae of known age at death and sex. Six dimensions (maximum height, maximum breadth, maximum thickness, height of the articular facet, lateral articular facet width, and medial articular facet width) were measured using a sliding digital calliper.</p> Results <p>Maximum height (<i>t</i>-test, <i>p</i> = 0.008) and maximum thickness (<i>t</i>-test, <i>p</i> = 0.014) were the only measurements that showed statistically significant side differences. However, all six patellar measurements from both sides were significantly greater in males than in females (<i>t</i>-test, <i>p</i> &lt; 0.001). After applying discriminant functional analysis to patellar measurements, the combination of all six measures provided the highest sex estimation accuracy on the right side (86.5%), whereas the combination of maximum height and maximum breadth provided the highest accuracy on the left side (90.4%). After applying all derived discriminant functions to estimate sex from measures taken on the contralateral side, the estimation accuracy for most of the functions decreased with statistical significance (<i>p</i> &lt; 0.05).</p> Conclusion <p>These results demonstrate that patellar siding is an important factor worthy of consideration when estimating the sex of unidentified human remains. Henceforth, it is advised to develop and apply separate discriminant functions for the left and right patella.</p>