Objective and useful mobility assessment of patients with arthropathy of the hip and knee.

Walking ability was objectively assessed by measurements of endurance, oxygen consumption, and pulse rate response. Twenty-four control subjects and 38 patients with arthropathy of the hip or knee were asked to walk on a treadmill, initially at 1 km/hour, for four minutes. The speed was increased by 1 km/hour every four minutes, until the subjects has walked for four minutes at 7 km/hour, or until they could not continue. Oxygen consumption, heart rate, cadence, and step length were measured. The controls could all walk for 1400 m, reaching a walking speed of 6 km/hour, and showed a consistent relation between heart rate, oxygen consumption, and speed of walking. The majority of arthritic patients failed to reach either this distance or speed. They had a significantly increased metabolic cost, and there was a good correlation (r = 0.65 to 0.99) between the changes in pulse rate and oxygen consumption in each individual patient. The endurance, heart rate response, and oxygen consumption changes shown by patients proved to be reproducible characteristics in patients whose disease was static.