The objective of this study was to assess the usability and safety of BION injectable neuromuscular microstimulators for therapeutic electrical stimulation (TES) to treat two conditions involving disuse atrophy: poststroke shoulder subluxation in hemiplegic subjects and knee osteoarthritis. Clinicians were provided with PC-based software to track implants and to design the exercise programs. Subjects self-administered TES (3 sessions/day, 10-30 min/session) for 6 or 12 weeks. Outcome measures included subluxation for the shoulder study and knee function and pain for the osteoarthritis study. All subjects were comfortable with the BION equipment and therapy; eight of 10 experimental subjects elected to continue treatment after the study period. Shoulder subluxation was reduced by 55% ± 54%; knee function was enhanced by 65% ± 24%; and knee pain decreased by 78% ± 18%. The devices did not migrate and did not cause inflammation or pain. Thresholds were stable over time. We conclude that the use of BION implants to exercise atrophic muscles was well-accepted and provided effective rehabilitation in these two clinical conditions.