Warm-up effect on active and passive arthrometric assessment of knee laxity

Objective: To determine the influence of a warm-up protocol suitable for use in clinical settings on tibial displacement and muscle activity during arthrometric knee laxity assessment. Design: Intervention study in which the subjects served as their own controls. Setting: The Biomechanics Research Laboratory, University of Wollongong, Wollongong, New South Wales, Australia. Subjects: Ten volunteers who reported no history of knee trauma or disease. Intervention: A warm-up consisting of 10 minutes of ergometer cycling (60rpm) followed by two sets of three hamstring muscle stretches. Main Outcome Measures: Outcome measures were: (1) anterior tibial translation and knee extension force assessed using a Dynamic Cruciate Tester® for each subject's right knee during active and passive testing, and (2) intensity of quadriceps and hamstring muscle activity during knee laxity testing. Results: There was significantly less quadriceps activity after warm-up ( t = 2.419, p = .039). However, there was no significant difference between anterior tibial translation, knee extension force, or hamstring muscle activity results before and after warm-up in either active or passive tests. Conclusion: A warm-up suitable for use in a clinical setting is not required before arthrometric assessment of knee laxity.