Measures of arch height and their relationship to pain and dysfunction in people with lower limb impairments.

BACKGROUND AND PURPOSE

Debate surrounds the theory that foot structure, and more specifically, the attitude of the midfoot as typified by the longitudinal arch, is associated with complaints of pain and injuries of the lower extremity. Recently, two simple clinical measures of arch height, the arch ratio (AR) and the longitudinal arch angle (LAA), have been reported as valid and reliable in the literature. The LAA has been found to approximate the lowest point of the arch during walking and running while the main strengths of the AR are that the measure takes into account foot size and arch mobility. We modified the AR so that the modified AR (mAR) would be measured in a similar fashion as the LAA to investigate if this new measure, which would account for foot size, correlated well with an established measure (LAA) that estimated the behaviour of the arch with walking and running. Also, we hoped to contribute to the literature correlating longitudinal arch height with pain - numeric pain rating scale - and dysfunction - Lower Extremity Functional Scale (LEFS) and Single Assessment Numeric Evaluation (SANE).

METHODS

Thirty-five subjects for this prospective correlational study were recruited from a community based outpatient practice that was part of a tertiary care academic medical centre. Reliability and validity of our investigator and of the mAR was first examined. We then examined the correlation of the clinical classification of arch height (high, normal, or low) produced by these two measures with each other. We also explored the correlation of multiple measures of dysfunction and pain with arch height.

RESULTS

Intrarater reliability and validity of the LAA showed an intraclass correlation (ICC) of 0.978 and Pearson's correlation coefficient (PCC) of 0.885, respectively. Intrarater reliability and validity of the mAR showed an ICC of 0.961 and PCC of 0.827, respectively. The LAA and our new measure, the mAR, were correlated with each other. The self-report measures of general health and activity level were significantly positively correlated (PCC = 0.598). Also significant and positively correlated were the LEFS and the SANE (PCC = 0.617), two measures of function.

CONCLUSIONS

Pain and dysfunction may be positively correlated but longitudinal arch height does not predict either pain or dysfunction.