THE note sent by a doctor to several executives at Johnson & Johnson was blunt: an artificial hip sold by the company was so poorly designed that the company should slow its marketing until it understood why patients were getting hurt.

The doctor, who also worked as a consultant to Johnson & Johnson, wrote the note nearly two years before the company recalled the device in 2010. And it was far from the only early warning those executives got from doctors who were paid consultants. Still, the company’s DePuy orthopedic unit plowed ahead, and those consultants never sounded a public alarm to other doctors, who kept implanting the device.

The memos have recently emerged during the trial of the first of more than 10,000 patient lawsuits brought against Johnson & Johnson over the hip implant device, the Articular Surface Replacement, or A.S.R. The company has insisted that it acted responsibly in determining when to halt its sale. But plaintiffs’ lawyers have offered a portrait of executives who put profits ahead of patients, even scuttling a plan to fix the implant because it cost too much.

It might not be surprising to find that executives acted to protect a company’s bottom line. Still, the Johnson & Johnson episode is also illuminating a broader medical issue: while experts say that doctors have an ethical obligation to warn their peers about bad drugs or medical devices, they often do not do so.