Joint loading in the presence of torsional deformities is overestimated unless gait adaptations are considered: a predictive simulation approach

Research indicates that lower-limb torsional deformities significantly impact joint loading, but the extent of this influence varies among studies, likely due to the distinct simulation methods employed. In this study, predictive simulations were utilized to examine the effects of femoral neck anteversion (FNA) and external tibial torsion (ETT) on hip and knee joint loading.

Using a modified adult musculoskeletal model, researchers generated simulations with alterations to FNA (ranging from 1° to 48°) and ETT (12° to 53°) individually and in combination, while maintaining a consistent walking speed of 1.33 m/s.

The simulations effectively replicated the adaptations in hip rotation and foot-progression angle observed in individuals with torsional deformities. Researchers calculated the compressive, shear, and resultant contact forces at the hip and knee joints, employing multiple linear regressions to determine the independent associations of FNA and ETT with each outcome.

The regressions accounted for 23%-86% of the variation in hip loading and 5%-87% in knee loading. The findings revealed that FNA generally contributed the largest relative amount to the variance in joint loading across the regression models, although the direction of these associations differed.

Specifically, a 10° increase in FNA led to a reduction of 0.076 BW in the first hip compressive peak and 0.035 BW in the resultant peak. Additionally, hip shear force showed the most substantial increase, averaging 0.055 BW across both peaks. In the knee joint, most loads also increased, peaking at up to 0.131 BW for the second resultant peak.

These associations with ETT were primarily observed at the second peak. The study concludes that accounting for gait adaptations resulting from torsional alterations is vital when estimating lower-limb joint loading, as overlooking these adaptations might lead to an overestimation of joint kinematics and external forces in individuals with lower-limb torsional deformities.