Comparison of ultrasonically applied vs. intra-articular injected hydrocortisone levels in canine knees

Phonophoresis of hydrocortisone is a commonly performed treatment for a wide variety of soft-tissue as well as intra-articular musculoskeletal disorders. There have been no previously reported studies indicating the degree of hydrocortisone penetration into joints achieved by means of phonophoresis. Twenty-four purebred greyhounds were used to compare intra-articular levels of hydrocortisone resulting from intra-articular injection, phonophoresis, and external application of hydrocortisone. A total of 40 samples from canine knees were analyzed by means of fluorescence polarization. Intra-articular hydrocortisone levels obtained with phonophoresis were extremely low in comparison with those obtained with intra-articular injection. There were no statistically significant differences in intra-articular hydrocortisone levels between the phonophoresis and external application treatments, or between either of these and placebo control measurements taken from knees of untreated dogs and from shoulders of treated dogs. It appears that phonophoresis is an ineffective method of obtaining hydrocortisone penetration into a joint in the canine model.