Comparison of three methods of assessing strength imbalances at the knee

Three strength measurement methods for determining muscle imbalances at the knee were compared in 24 male athletes. Peak quadriceps extensions and hamstring flexions were measured isotonically, isometrically, and isokinetically. Isokinetic measurement was performed at 60, 180, and 300 degrees /sec. Repeated measures ANOVA revealed no significant difference among the three methods for bilateral imbalance ratio measurement. However, hamstring/quadricep ratios were significantly greater when measured isokinetically than when measured by the other methods. It was concluded that strength measurement methods may be used interchangeably when determining bilateral strength imbalance ratios at the knee but they may not be used interchangeably when assessing hamstring/quadricep ratios. Determinations of excess imbalance ratios (>10%) showed no consistent pattern across methods and may indicate problems associated with attempts to identify safety limits from muscle testing.J Orthop Sports Phys Ther 1988;10(4):134-137.