Static Frontal Plane Tibiofemoral Alignments and Their Effects on Knee Biomechanics During Level Walking and Stair Ascent Tasks

Knee osteoarthritis is a degenerative joint disease that can onset due to abnormal knee adduction moments (KAMs), which are related to frontal plane knee joint alignment. Gait modifications including toe-in (TI) and wider step widths have been proposed as individual intervention strategies, but have not been previously combined, to reduce abnormal frontal plane loading in healthy and osteoarthritic populations. Study One investigated clinical based measurements to predict radiographic frontal plane knee joint alignment, measured as the mechanical axis angle (MA). Study Two compared three different hip joint center estimation methods on MA predictions using three-dimensional motion capture. Study Three and Study Four compared normal, TI, and toe-in with wider step width (TIW) gait modifications during level walking and stair ascent, respectively, in varus, neutral, and valgus knee alignment groups. Forty healthy participants participated in Study One and thirty-eight in studies Two, Three, and Four. Anteroposterior full-limb long standing radiographs were used to determine varus, neutral, and valgus knee alignment groups. A three-dimensional motion analysis, force platforms, and an instrumented 3-step staircase were utilized to collect walking and stair ascent trials.

Study One showed a combination of caliper, malleolar width, and thigh length measurements accurately predict radiographic MA. Study Two showed each motion capture hip joint center estimation method result in only slight non-significant variations in MA predictions, and thus each are valid in usage for motion capture based MA predictions. Study Three found the TIW gait modification can reduce 1^st peak KAMs during normal level walking in all three alignment groups, without subsequent increases in 2^nd peak KAMs found using toe-in only. Study Four found the TIW gait could reduce both 1^st and 2^nd peak KAMs compared to normal stair ascent gait.

Frontal plane knee joint alignment can be accurately predicted using a combination of clinical measurements, as well as motion capture with different methods of predicting hip joint center locations. The TIW gait can reduce frontal plane knee joint loading during level walking and stair ascent. The effectiveness of the TIW gait modification in varus knee alignments indicates this may be a viable option for future knee osteoarthritic patients.