90 patients with mild to moderate knee osteoarthritis (Kellgren-Lawrence grade I-II) were randomized to receive either a low intensity, long duration ultrasound device or a sham ultrasound device. Treatment was administered daily for 6 weeks. Outcome measures included pain on a numeric rating score (NRS pain), pain, stiffness, and function scales of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), range of motion in flexion and extension, and strength in flexion, extension, and rotation. Results after 6 weeks demonstrated significantly greater improvement from baseline in the US group compared to the sham group for NRS pain, WOMAC pain, WOMAC stiffness, and WOMAC function scales. Differences between groups in range of motion and strength measures were not statistically significant.