A prosthesis is an artificial replacement of or substitute for a part of the body. Prostheses may be removable or may be permanently implanted. A prosthesis is used for functional or cosmetic reasons or in many cases, a prostheses is used for both. Hip and knee prostheses are permanently implanted to replace a hip or knee that was not functioning properly or has had years of wear and tear from an individual. Hip and knee replacements are among the most common surgical procedures in all of orthopedic surgery. The procedure involves replacing damaged or deteriorated joints with artificial replacements, which include parts made of high molecular weight polyethylene, similar to pliable plastic. Most patients who undergo a hip or knee replacement gain improved agility, flexibility, and reduced pain; however, due to the practice of sterilizing polyethylene, some replacements have failed prematurely, resulting in injury, and causing the need for further surgery to replace the failed parts. Several companies use a technique known as gamma irradiation in air to sterilize the hip and knee prostheses. This sterilization process has caused the polyethylene part of the devices, once implanted in the body, to break into small pieces which then can lodge into the patient's hip or knee joint. In the body's fight to rid itself of those pieces, the immune system can also attack the patient's healthy bone, causing it to decay, a condition known as osteolysis. The patient inevitably needs another potentially risky surgery to replace the hip or knee prosthesis long before expected. Certain hip and knee implants that were manufactured beginning in the early 1990s by the following manufacturers are being investigated for the failure described above: . Depuy . Howmedica Osteonics Corp. . Howmedica, Inc. . Osteonics Corp. . Zimmer . Biomet Each hip and knee prostheses case is unique and requires a thorough review of the individual's medical records to determine proper product identification and to determine potential damages or injuries as a result of the implantation of a hip or knee prosthesis. If you or someone you know have undergone hip or knee replacement, you may be eligible to participate in hip and knee replacement litigation. In which case, if you are eligible, it is advisable to contact an experienced knee and hip prosthesis law firm to learn about the legal details involved with developing a case. In such a case, the plaintiff will seek compensatory damages from the defendant for medical bills.