The floodgates appear ready to open in litigation regarding recalled DePuy ASR hip replacements.

According to a Wall Street Journal report, about 1,000 lawsuits have been filed in federal and state courts accusing the Johnson & Johnson of knowing about problems with some of its metal-on-metal hip joints before its DePuy Orthopaedics Inc. unit stopped making ASR hip implants in 2009. J&J, which finally recalled the joints world-wide in August 2010, denies the allegations and is fighting back.

DePuy’s only comment was that J&J boosted its reserves for product-liability costs, for products including the recalled hip joints, by $570 million last year. In addition, J&J, which had 2010 sales of $61.6 billion, has put aside about $280 million to cover surgeries and other medical care for patients with those joints.

Many of the hip-joint lawsuits have been consolidated in federal court in Ohio. Some plaintiff’s lawyers are pushing for the court to certify the plaintiffs in the case as a class, whose complaints can be combined into a single lawsuit.

One plaintiffs’ attorney told The Wall Street Journal that J&J has turned over more than 200,000 of the nearly 18 million pages of internal documents it is expected to submit.

Litigation this size is a big business, often producing multimillion-dollar settlements and sometimes similarly large jury verdicts for plaintiffs. Defense attorneys, meanwhile, can rack up huge bills for their services during the long-running cases.