## 4 Discussion  
This study compared three ankle joint models with an increasing level of personalization to evaluate their anatomical consistency, defined as their capability of fulfilling the hypothesis of workless motion, and hence assess their credibility. The reported results proved that anatomical consistency increases with the level of personalization of the joint model. On the cohort, SGJ showed elongation of the FiCa ligament up to 20%, associated with a highly non-physiological behavior. Both the fixed rotational axis of MFJ and SGJ resulted in considerable cartilage co-penetration during dorsiflexion, with the SGJ reaching up to \(-\)4.1 mm. The effects of joint personalization were more evident when looking at single individuals: MCJ showed good anatomical consistency for each of the modeled dataset; MFJ exceeded the experimental threshold of 5% of ligament isometric elongation, still remaining within physiological range, however, resulting in a \(-\)2.4 mm maximum of cartilage co-penetration; SGJ simply resulted in ligament elongation and cartilage co-penetration not compatible with the ankle physiology. When included within a subject-specific MSK model of the lower-limb, the three ankle joints caused only small, yet significant, differences in the overall limb kinematics (Figure 4A). Similarly, small but significant differences could be found for joint torques (Figure 4B) Differences were more evident when analyzing the muscles: the M1\({}_{\text{SG}}\) predictions were overall significantly higher than those from the other two models, with a maximum difference above 1.4 BW at the soleus. M1\({}_{\text{MF}}\) and M1\({}_{\text{MC}}\) performed similarly on the cohort, with minor differences for the peroneal muscles (Figure 4C). When the effects of anatomical inconsistency are made explicit by introducing the joint internal forces associated with ligament and cartilage deformations (Figure S1), the MSK model output changed considerably. M2\({}_{\text{SG}}\) did not converged in six cases and outputs were altered to non-physiological values and patterns. Some muscle forces (Tibialis Posterior and Peroneal), ankle joint contact forces and ankle moments associated to M2\({}_{\text{MF}}\) and M2\({}_{\text{MC}}\) changed significantly as a result of accounting for the tissue deformations (Figure 5C,D). The introduction of internal forces also altered the results for the individual participants at the joint moments and the muscle and joint contact forces (Table 2). For SGJ, maximum individual differences between M1 and M2 was 13.3 N/Kg for the ankle moment, 2.5 BW \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Joint Model** & \multicolumn{2}{c}{**Max Difference between M1 and M2**} \\ \cline{3-4}  & & **Cohort Values** & **Individual Values** \\ \hline \multirow{3}{*}{Ankle joint moment (N/Kg)} & **SGJ** & 3.7 & 13.3 \\  & **MFJ** & 0.0 & 0.1 \\  & **MCJ** & 0.0 & 0.0 \\ \hline \multirow{3}{*}{Hip JCF(BW)} & **SGJ** & 0.5 & 1.3 \\  & **MFJ** & 0.0 & 0.1 \\  & **MCJ** & 0.0 & 0.0 \\ \hline \multirow{3}{*}{Knee JCF (BW)} & **SGJ** & 1.1 & 2.5 \\  & **MFJ** & 0.0 & 0.1 \\  & **MCJ** & 0.0 & 0.0 \\ \hline \multirow{3}{*}{Ankle JCF (BW)} & **SGJ** & 43.5 & 120.8 \\  & **MFJ** & 2.2 & 6.9 \\  & **MCJ** & 0.1 & 0.8 \\ \hline \multirow{3}{*}{Soleus (BW)} & **SGJ** & 3.6 & 2.5 \\  & **MFJ** & 0.2 & 0.2 \\  & **MCJ** & 0.0 & 0.0 \\ \hline \multirow{3}{*}{Gas med (BW)} & **SGJ** & 1.0 & 0.5 \\  & **MFJ** & 0.0 & 0.1 \\ \cline{1-1}  & **MCJ** & 0.0 & 0.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Maximum ligaments elongations and cartilage co-penetration over the ROM for the average cohort and individuals. for the Soleus force and 120.8 BW for the ankle contact force. MFJ was more stable, reaching however a maximum individual difference for the ankle contact forces of 6.8 BW. MCJ was less affected, with an maximum individual difference for the ankle contact forces of 0.8 BW.