Therapeutic ultrasonography uses sound waves to produce deep-tissue heating. (There are nonthermal effects as well, but these effects are not usually used therapeutically for musculoskeletal disorders.) Administered by a licensed provider, it reduces pain and maximizes function. The sound waves are absorbed in tissues having high collagen content, so in
areas where bony surfaces are prominent, a pulsed rather than continuous mode should be used to avoid damaging tissues (pulsed ultrasonography reduces the risk of burning by administering the sound waves in small bursts). Heating occurs primarily at tissue interfaces (such as bone and soft tissue), although sound waves may penetrate 7 to 8 cm of fat There have been few high-quality clinical trials examining the benefits of ultrasonography in rehabilitation. Rutjes
and colleagues conducted a systematic review of five RCTs or quasi-RCTs that compared therapeutic ultrasonography
with a sham intervention or no intervention in patients with knee OA Data from 341 patients were synthesized. Two trials evaluated pulsed ultrasound, two evaluated continuous, and one both pulsed and continuous ultrasound.
The outcomes examined included pain, physical function, and disability (as determined using the Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]). The intervention groups experienced improvements in self-reported pain measured on a visual analog scale (SMD, −1.2 cm; 95% CI, −1.9 to −0.6) and in function (SMD, −1.3 units
on the 1-to-10 WOMAC disability scale; 95% CI, −3 to 0.3). No adverse events were reported. The authors noted that there was a high degree of heterogeneity among the trials for the outcome of function (88%).