Effects of Ultrasound and Stretch on Knee Ligament Extensibility

Braden C. Fleming, Nancy J. Zimny, Brian V. Reed, Takamaru Ashikaga

Study Design: Randomized, double blind pre-test and post-test with repeated measures. Objective: To determine whether heating with continuous wattage ultrasound (CWUS) augmented the effects of stretching on ligament extensibility in nonimpaired human subjects. Background: Heating with CWUS, combined with static stretching, is often used to treat ligament "tightness," but "heat and stretch" has not been studied well in vivo. Methods and Measures: Twenty-one nonimpaired women subjects (aged 31.5 ± 11.0 years) underwent serial measurements of knee joint displacement (valgus and varus) on a Genucom arthrometer before and after valgus stretch (10 ft-lb x 2.5 minutes). Subjects received either simultaneous CWUS (3 MHz, 1.25 W/cm2) or sham CWUS applied over the medial collateral ligament. Five trials (2 before, 3 after treatment) were conducted with the right knee positioned in 20° of flexion. Subjects received the alternate treatment 28 days later. For each subject, the same investigator performed all testing. Results: Repeated measures ANOVA revealed that stretching, combined with sham CWUS, increased mean valgus displacement from 8.95° (±1.72°) to 10.00° (±2.10°). Stretching, combined with CWUS, increased mean valgus displacement from 9.24° (±2.36°) to 10.48° (±2.54°). This was a 13.4% change from the control condition. Conclusion: Heating with CWUS did not augment the effects of stretching. "Heat and stretch" with CWUS may not be more effective than stretching alone for increasing the extensibility of dense connective tissue. J Orthop Sports Phys Ther. 2000;30(6):341-347. Key Words: connective tissue, heat, stretch, ultrasound

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