Quantitative test of knee laxity in Chinese.

Anterior knee laxity of 100 Chinese male subjects who had no history of previous injuries to their knees was examined with an instrumented knee arthrometer (MEDmetric Knee Arthrometer, model KT-1000). Two measurements were used to evaluate the anterior laxity: 1) anterior displacement produced by anterior force of 89 newtons (20 lbs); and 2) anterior compliance index (ACI), the displacement difference between an anterior force of 89 newtons (20 lbs) and 67 newtons (15 lbs). All knees were examined at a flexion angle of 20 +/- 5 degrees and an external tibial rotation of 10 +/- 5 degrees with the use of thigh and foot supports. The mean anterior displacement for the right and left knee were 4.5 +/- 2.0 mm and 4.3 +/- 1.9 mm, respectively, while 84% of the study subjects had right and left differences (anterior displacement difference, ADD) of less than 2 mm. The anterior compliance index was 0.85 +/- 0.4 mm for the right knee and 0.78 +/- 0.33 mm for the left knee. The mean anterior compliance index difference (CID), that is the difference between the right and left ACI, was 0.25 +/- 0.3 mm. A total of 93% of the subjects had a difference in the right-left CID of less than 0.5 mm. Variation between the right and left knee does exist, but the difference is not statistically significant (p > 0.05). Therefore, comparison of the right-left ADD and CID can be a useful reference in the assessment of a ligamentous injury.