ObjectiveTo study the difference of femoral condylar twist angle (CTA) measurement in three dimensional (3-D) reconstruction digital models of human knee joint based on the two dimensional (2-D) images of MRI and CT so as to provide a reference for selecting the best method of CTA measurement in preoperative design for the femoral prosthesis rotational position. MethodsThe CTA of 10 human cadaveric knee joint was measured in 3-D digital models based on MRI (group A), in 3-D digital models based on CT (group B), in the cadaveric knee joint with cartilage (group C), and in the cadaveric knee joint without cartilage (group D), respectively. The statistical analysis of the differences was made among the measurements of the CTA. ResultsThe CTA values measured in 3-D digital models were (6.43±0.53)° in group A and (3.31±1.07)° in group B, showing significant difference (t=10.235, P=0.000). The CTA values measured in the cadaveric knee joint were (5.21±1.28)° in group C and (3.33±1.12)° in group D, showing significant difference (t=5.770, P=0.000). There was significant difference in the CTA values between group B and group C (t=5.779, P=0.000), but no significant difference was found between group A and group C (t=3.219, P=0.110). ConclusionThe CTA values measured in the 3-D digital models based on MRI are closer to the actual values measured in the knee joint with cartilage, and benefit for preoperative plan.