Measurement of circumference of the knee with ordinary tape measure

The circumference of the knees and thighs at three locations was measured in 10 patients on two consecutive occasions by three observers. Analysis of the results for interobserver, intraobserver and among-patient variation established that a change in circumference noted by different observers on two different days is significant if it exceeds 1-5 cm at the midpatella, 2-7 cm at 7 cm above, and 3-5 cm at 15 cm above the patella. If a single observer performs both measurements, the change need exceed only 1-0, 2-0, and 2-7 cm, respectively, to be significant.