The purpose of this study was to investigate the effect of ultrasound and shortwave diathermy, with and without therapeutic exercise on osteoarthritic (OA) knees. From February 1987 to January 1989, we collected 94 OA knees from 61 female patients and divided them into 4 groups. Group 1 received ultrasound therapy, group 2 had shortwave diathermy, group 3 received ultrasound and an exercise program, and group 4 received shortwave diathermy and exercise therapy. All 61 patients (94 knees) were assessed by functional incapacity scoring and isokinetic testing before and after treatment. At the termination of treatment, all patients had significant improvement in both functional capacity and peak torque. This study failed to prove any significant difference in treatment effect between ultrasound and shortwave diathermy for chronic OA knees. However, the exercise program in addition to the diathermy did promote the treatment effect in both function and muscle torque.