46 patients with mild to moderate knee osteoarthritis were randomized to 2 weeks treatment of either phonophoresis (PhP), using ultrasound and 0.5% piroxicam gel, or to ultrasound treatment alone (UT). The study investigated the effects of phonophoresis in improving knee function and pain, by promoting the absorption of non-steroidal anti-inflammatory drug (NSAID) using an ultra-sound. Post-treatment Visual Analog Scale (VAS) pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores significantly reduced in PhP group compared to ultrasound only. Total WOMAC, representing functional improvement, also improved over time, but did not differ between the two groups.