The effects of heating with ultrasound on knee joint displacement.

Abstract

Heating with continuous wattage ultrasound combined with mobilization procedures is often used to treat ligament "tightness," but the effects of heat on ligament extensibility have not previously been studied in vivo. To address this problem, 25 young adults underwent knee joint displacement tests on a Genucom arthrometer before and after continuous wattage ultrasound (1 MHZ, 1.5 W/cm2 x 8 min). Preultrasound intrarater reliability (ICC; N = 11) was 0.87-0.98 for varus/valgus and recurvatum tests and 0.70-0.73 for anterior-posterior drawer tests. Continuous wattage ultrasound was associated with small increases in mean varus/valgus excursion at 0 degree and 20 degrees of knee flexion (p < or = .04) and in recurvatum excursion (p < or = .04) but not in anterior-posterior drawer excursion. The magnitude of the changes was 1.3 degrees or less and represented relative changes of 6.1-9.8%. Continuous wattage ultrasound at common clinical intensities made some knee ligaments slightly more extensible in normal subjects, although the magnitude of the effect was not deemed clinically significant.