Inter- and intra-examiner reliability of leg-length differential measurement: a preliminary study

The phenomenon of "short leg" has long been used and debated clinically. A uniquely chiropractic measurement technique was not studied in any of the few studies of reliability of measurement which have been reported. An inter- and intra-examiner reliability study was therefore performed to validate a prone leg length-differential test. Naive students (n = 40) were called, in random order, into three adjacent examining rooms where three experienced chiropractic clinicians measured differential leg lengths. Using standard placement a tape measure was read to the nearest mm to detect inequalities at the shoe-sole interface. The leg length differences were recorded, for both the straight and flexed legs prone positions, twice by each of the three clinicians. Intraclass correlations were significant for the two independent readings for all three examiners, indicating high reliability of the test. Good agreement among examiners was indicated as well by significant intraclass correlation in two of the three possible examiner combinations. These results argue strongly for the reality of the leg length inequality phenomenon and also that it can be reliably measured.