SPONTANEOUS AMBULATORY ACTIVITY AS A QUANTIFIABLE OUTCOME MEASURE FOROSTEOARTHRITIS OF THE KNEE

Objective. Quantifiable outcome measures for disabling diseases such a s osteoarthritis (OA) of the knee are necessary in order to compare th e impact of different interventions competing for financial resources. Current subjective and questionnaire data are not satisfactory for su ch study. In this study, we examine the potential of the direct measur ement of ambulatory activity as such a measure. Population. Patients w ith X-ray evidence of OA of the knee recruited to studies of anti-infl ammatory agents (n = 29). Patients with OA of the knee awaiting knee r eplacement surgery (n = 28). Methods. Comparison of various standard m easures with total energy output data from an activity monitor. Result s. Spearman rho correlations of ambulatory energy output (number of st eps x average amplitude of steps) correlated with other measures. Corr elation with physician's opinion was greater than with patient's opini on (r = 0.4 and 0.2, respectively). There was no correlation with visu al analogue pain scale or OA severity index. Correlation with scales o f the Nottingham Wealth Profile questionnaire were not significant eit her for mobility (r = - 0.15) or for pain (r = - 0.13). There was, how ever, a significant correlation between poor sleep and increased activ ity (r = 0.34, P < 0.05). Correlation with Kellgren X-ray grade was si gnificant (r = - 0.45, P = 0.01). Patients recruited to anti-inflammat ory studies were 69% more active than those awaiting replacement surge ry. Conclusion. The monitoring of ambulatory activity shows some const ruct and discriminant validity, and is worthy of further study.