The hip adduction moment as a proxy for joint loading: a comparison between walking and running

Area of Science:

• Biomechanics
• Orthopedics
• Human Movement Science

Background:

• Hip adduction moment (HAM) is a common proxy for hip joint loading.
• The validity of HAM as a surrogate for hip joint reaction force (HJRF) across various gait tasks and modifications is not well understood.
• Understanding gait modification effects on hip loading is crucial for managing hip osteoarthritis.

Purpose of the Study:

• To investigate the relationship between HAM and HJRF during walking and running.
• To examine how foot progression modifications influence this relationship in healthy adults.
• To assess the validity of HAM as a surrogate for HJRF under altered gait conditions.

Main Methods:

• Utilized musculoskeletal modeling (OpenSim) to estimate HJRF.
• Applied inverse dynamics to calculate HAM.
• Employed Spearman correlations and mixed-effects models to analyze data from natural and modified gaits (toe-in walking, toe-out running).

Main Results:

• During walking, HAM strongly correlated with HJRF in both natural and toe-in conditions, with toe-in reducing both measures.
• During running, peak HAM showed a significant correlation with HJRF in the natural condition but not in toe-out running.
• Toe-out running decreased HAM but did not significantly alter HJRF, indicating a decoupling of these measures.

Conclusions:

• Gait modification significantly alters the relationship between HAM and HJRF, especially during dynamic activities like running.
• HAM is a valid indicator of hip loading during normal walking but less so under modified dynamic conditions.
• Single-plane moments may not fully represent joint loading during altered gait, highlighting limitations in using HAM as a sole surrogate for HJRF.