Daily walking and the risk of incident functional limitation in knee osteoarthritis: an observational study

White DK, et al. · Arthritis Care & Research

Each extra 1,000 steps a day was associated with a 16% lower risk of incident functional limitation by gait speed and 18% by self-reported WOMAC function two years later, adjusted for age, sex, race, education, BMI, comorbidity, depressive symptoms, widespread pain, knee pain severity, radiographic knee OA and study site. Thresholds of under 6,000 steps (gait speed) and under 5,900 (self-report) best separated those who developed limitation, though the separation is modest: sensitivity and specificity of 67.3% and 71.8% for the first, 58.7% and 68.9% for the second. More walking predicted better, not worse, outcomes.

Population

1,788 adults (mean 67) with or at risk of knee OA, objectively measured steps

Intervention

Exposure: accelerometer-measured daily steps over 7 days

Comparator

Across step counts

Limitations

Observational; reverse causation - healthier people walk more - is only partially controllable, and the outcome is function rather than joint structure. Few events to work from: 113 of 1,381 developed limitation by gait speed and 63 of 1,422 by self-report. The authors describe the step thresholds as preliminary and say they should be tested in trials before being read as targets. NIH-funded.