To ask the Secretary of State for Health how NHS hospitals, carrying out private treatment for the replacement of knee and hip joints, account for the parts used for (a) private treatment and (b) NHS treatment. 
National health service trusts purchase their hip and knee prostheses direct from suppliers. Consultants will make a clinical decision on the actual implant required for each patient, and some will have a preference on the make of implant they use. The implants for both NHS and private patients would come from the stock the trust has in store. Private patients or their insurers will be invoiced by the NHS trust for the care that they have received.Details of the hip replacement operation for both NHS and private patients should then be entered on the National Joint Registry. This will assist NHS trusts to identify the any patients with a particular make of hip or knee if there is concern about the performance of the implant.