[Forces and turning moments of hip and knee joints in locomotion]

In order to be helpful to orthopedic surgeons in planning operations, and providing quality control, gait analysis must provide information on forces and moments at major joints because kinematic data alone have proved to be unsatisfactory. A practical procedure for this purpose was developed and applied to 20 children and young adults, using the inverse dynamic approach. Segmental body volumes were obtained by stereophotogrammetry. Together with density values, this permits individual calculation of segmental mass center positions even in the presence of severe deformity. Segmental anatomical coordinate systems were defined and tagged by skin markers. Subsequent stereophotogrammetric gait recording by high-speed cameras and 3D force plates allowed the calculation of reactive forces and moments with their changing values over each gait cycle. For the two peaks of force transmission in the early and late stance phases, vector diagrams demonstrate 3D components of forces and moments as related to the anatomy of the thigh and shank of a normal young adult. The peak reaction force component in the longitudinal axis during initial loading about reaches body weight, the anteroposterior force 2/5th and the mediolateral component 1/25th of body weight.