PURPOSE: A recent novel application of ultrasound (US) therapy is in the treatment of bone fractures. Specialized US units have been shown to accelerate the rate of fracture repair by 30–38%. While these units are highly efficacious, their cost is currently prohibitive in sports medicine. It has been questioned whether conventional therapeutic US units as traditionally used by physical therapists may be used during fracture repair to elicit a similar effect. The aim of this study was to investigate the effect of US produced by a conventional therapeutic US unit on fracture repair in an animal model. METHODS: Thirty adult male Long-Evans rats underwent surgery to create bilateral midshaft femur fractures. The femur was fractured by way of a transverse osteotomy and stabilized using a stainless steel intramedullary K-wire. US therapy was commenced the first day following fracture induction and introduced 5 days/wk. Each animal was treated unilaterally with active-US and contralaterally with inactive-US. Active-US had a 2-ms burst of 1.0-MHz sine waves repeating at 100 Hz. The spatial-averaged, temp oral-averaged intensity was set at 0.1 W/cm2. Animals were killed at 25 and 40 days following fracture induction, and the fractures assessed using radiography, dual energy X-ray absorptiometry, peripheral computed tomography and destructive mechanical testing (four-point-bending). RESULTS: There were no significant differences between active- and inactive-US treated fractures for any measure when assessed at 25 days (all p>0.05). In contrast, at 40 days active-US treated fractures had 16.9% (95% CI, 2.3 to 31.4%) greater bone mineral content at the fracture site than in inactive-US treated fractures (p<0.05). This increase did not result from an increase in the amount of bone mineral per unit volume (P=0.14). Rather, it resulted from an increase in bone size, with active-US treated fractures having 25.8% (95% CI, 3.9 to 47.6%) greater bone area than in inactive-US treated fractures (p<0.05). The elevated fracture site bone mass at 40 days resulted in active-US treated fractures having 81% (95% CI, 0.8 to 162.7%) greater strength and 65.6% (95% CI, 7.6 to 123.6%) greater stiffness than inactive-US treated fractures at this time point (all p<0.05). CONCLUSIONS: This study found fractures treated with US therapy to have greater bone mass and strength than non-US treated fractures. This confirms previous studies demonstrating a beneficial effect of US on fracture repair, and indicates that US produced by a conventional therapeutic US unit as used by physical therapists may be used to accelerate fracture repair. This latter finding requires clinical investigation.