The Johnson antishear device and standard shin pad in the isokinetic assessment of the knee.

Isokinetic training and assessment of the knee joint has been the mainstay of rehabilitation, especially in patients with anterior cruciate ligament deficiency. Besides the original shin pad used, the antishear device was introduced by Johnson in 1982. This device has been shown biomechanically to prevent excessive anterior translation of force on the tibia during training. However, there is a need to compare the antishear device and the standard shin pad in the isokinetic assessment. Hence, the major objective of this study is to define, if any, the difference in patient assessment between the new double pad device and the old single shin pad. Ten subjects with no previous history of injury on either knee were tested with the Cybex Isokinetic Dynamometer. There were four men and six women and the mean age was 25.2 years. They were randomized into different test sequences with different shin pads at different speeds. Correlation and paired t tests (P) were performed to find out the correlation and difference between the two devices. There was significant difference in performance assessment between the two devices in knee extension (P < 0.05) but no significant difference in knee flexion (P > 0.05). There was also a high correlation (r > 0.75) between the two devices. It is concluded that because of the significant difference of data generated between the two devices, it is important to select one single device with each patient during a series of testings.