Inter-observer reproducibility was excellent and there were no differences between Akagi, Dalury, and inter-eminence lines. Similarly, intra-observer reliability was excellent for Akagi, Dalury, and inter-eminence lines. Qualitative review of tibial inter-condylar eminences suggested that these could be easily identifiable. When taking the medial angle from a medial–lateral reference line, the Akagi line showed a mean of 96.90° (±10.27), inter-eminence line 94.52° (±12.84), and Dalury line 88.06° (±11.75). The angle produced by the Dalury line was significantly different from both the Akagi and inter-eminence lines (P ≤ 0.001). The Akagi line and inter-eminence line showed a strong correlation (r = 0.74). The Dalury line showed a weaker correlation with both the Akagi line (r = 0.69) and inter-eminence line (r = 0.40).