Effects of ultrasound and stretch on knee ligament extensibility

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 non impaired human subjects. Background: Heating with CWUS, combined with static stretching, is often us ed to treat ligament "tightness," but "heat and stretch" has not been studi ed well in vivo. Methods and Measures: Twenty-one nonimpaired women subjects (aged 31.5 +/- 11.0 years) underwent serial measurements of knee joint displacement (valgu s and varus) on a Genucom arthrometer before and after valgus stretch (10 f t-lb x 2.5 minutes). Subjects received either simultaneous CWUS (3 MHz, 1.2 5 W/cm(2)) or sham CWUS applied over the medial collateral ligament. Five t rials (2 before, 3 after treatment) were conducted with the right knee posi tioned in 20 degrees of flexion. Subjects received the alternate treatment 28 days later. For each subject, all testing was performed by the same inve stigator. Results: Repeated measures ANOVA revealed that stretching, combined with sh am CWUS, increased mean valgus displacement from 8.95 degrees (+/-1.72 degr ees) to 10.00 degrees (+/-2.10 degrees). Stretching, combined with CWUS, in creased mean valgus displacement from 9.24 degrees (+/-2.36 degrees) to 10. 48 degrees (+/-2.54 degrees). This was a 13.4% change from the control cond ition. Conclusion: Heating with CWUS did not augment the effects of stretching. "H eat and stretch" with CWUS may not be more effective than stretching alone for increasing the extensibility of dense connective tissue.