Date of Award

5-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Kinesiology and Sport Studies

Major Professor

Songning Zhang

Committee Members

Clare E. Milner, Jeffrey T. Fairbrother, Jeff Reinbolt

Abstract

Stair negotiation is one of the most challenging tasks for older adults especially for those suffering from knee osteoarthritis (OA). To date, no studies have investigated the effects of increased step width (SW) on knee joint biomechanics. The purpose of Study One was to investigate the effects of increased SW on peak internal knee abduction moment and other lower extremity variables during stair descent in healthy older adults. The purpose of Study Two was to investigate the effects of increased SW on peak internal knee abduction moment, knee pain and other lower extremity variables during stair descent in medial compartment knee OA adults. A motion analysis system and an instrumented staircase were used to collect lower extremity joint biomechanics in both studies. Participants performed five stair descent trials at their self-selected speed at preferred, wide and wider SW.

Study One: Twenty healthy adults (54.9±9.1 years) were recruited for this study. The preferred normalized SW in healthy adults during stair descent was 20% of leg length. The results indicated that increased SW during stair descent reduced 1st and 2nd peak internal knee abduction moments in healthy adults. These abduction moment reductions may be caused by a less adducted knee with increased SW. These results may have implications in reducing medial compartment knee loads in stair descent in healthy adults to potentially help prevent medial compartment knee OA onset.

Study Two: Thirteen medial compartment knee OA patients (62.5±9.0 years) were recruited for this study. Increased SW did not change subjective knee pain in knee OA patients. Preferred SW in knee OA adults during stair descent was 20% of leg length. The increased SW during stair descent reduced 2nd peak knee adduction angle but did not reduce peak internal knee abduction moments in knee OA patients. It appears that earlier timing of 2nd peak adduction angle with increased SW may be related to the unchanged 2nd peak abduction moment. Further studies investigating simulated muscle forces and compartmentalized joint forces in medial compartment knee OA patients during stair negotiation are warranted to obtain a more accurate depiction of medial knee joint loads.

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