The British government has struck a deal with Nuffield Hospital and Capio Healthcare to carry out 25,000 operations on patients from the NHS waiting list in England.
John Reid, the health secretary, will announce contracts with Nuffield Hospitals and Capio Healthcare to provide hip and knee replacements at 40 of their centres across England.
Under normal NHS practice there will be no charge to patients. These new NHS contracts will help reduce maximum waiting times to six months and generally pick up the slack caused by long NHS waiting lists.
Health is seen as one of the government's key components to winning the next general election.
Other private healthcare firms are thought to be furious that Nuffield, a not-for-profit charitable group, is using its spare capacity to undercut them so comprehensively.
Mr Reid told the Commons health select committee in October that NHS trusts buying operations in the private sector paid about 40% more than the standard NHS rate.
By negotiating the new contracts at a bulk rate, he is claiming to have eliminated that excess. Nuffield will start carrying out the operations next month and all 25,000 should be done by April next year. Further contracts may then be signed.
Patients needing orthopaedic surgery have endured some of the longest waiting lists in NHS history. The maximum wait in England has been cut to nine months and the target is to cut this to six months by the end of next year.