Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Health and Rehabilitation Sciences


Dr. Andrew M. Johnson


Leg length discrepancy is a condition shown to affect 25-70% of the general population. The ubiquitous nature of leg length discrepancy can prove frustrating to many clinicians, particularly due to lack of consensus surrounding the amount of discrepancy that necessitates treatment.

The present research is intended to address the uncertainty surrounding diagnostic and treatment thresholds, through three related studies. In the first study, leg length discrepancy was manipulated in a sample of 15 healthy young adults, using a novel heel-to-toe lift (creating discrepancies of 5mm, 20mm, and 30mm), and the effects of this new discrepancy was observed on the spatial-temporal parameters of gait. In the second study, leg length discrepancy was again manipulated (within a sample of 40 healthy young adults) in a similar fashion to the first study, and the effects of this discrepancy on both gait and balance were observed within a dual-task paradigm, wherein attentional capacity was manipulated using an ecologically valid secondary task (dialling numbers on a cellphone). Finally, in the third study, long-term gait adaptation was measured within a sample of 100 individuals (aged 25 to 76) that had undergone an high tibial osteotomy, and who had a surgically induced leg length discrepancy from this operation. This study used leg length discrepancy as a covariate in the model, to control for the extent to which post-surgical gait changes were the result of leg length discrepancy.

Taken together, the results of these three studies provide several important pieces of clinical information: (1) small discrepancies (as small as 5mm) can disrupt gait; (2) larger discrepancies (particularly when they are qualitatively obvious to the individual) may require conscious attention to the gait adaptation; (3) conscious gait adaptation may be be disrupted by attention-demanding secondary tasks; and (4) the effects of acquired leg-length discrepancy persist for as long as a year after they are induced.

These results are presented in the context of a “leg length accommodation model”, that incorporates perceptual aspects of the leg length discrepancy, and attentional capacity (for the accommodation of the discrepancy).