"Patients with rheumatoid arthritis are more likely to suffer hip dislocation after hip replacement surgery than those with osteoarthritis a new study says. In addition rheumatoid arthritis patients have a higher infection risk after total knee replacement than osteoarthritis patients the study authors found. Rheumatoid arthritis which is felt throughout the whole body is caused when a persons immune system attacks his or her own tissues. Osteoarthritis which is usually felt only in the joints is caused by wear and tear on the body. For the study the investigators analyzed the findings of  studies published between January  and December . The studies included arthritis patients aged  or older who had hip or knee replacements. The findings are published in the Nov.  online edition of Arthritis  Rheumatism. Joint arthroplasty is successful in relieving the pain and disability caused by hip or knee arthritis study author Dr. Bheeshma Ravi from the University of Toronto and Womens College Research Institute said in a journal news release. While complication rates are low there are some cases with serious consequences that include infection joint dislocation blood clots and even death. The study team found no differences between the two groups of arthritis patients in rates of followup surgery or day blood clot or death risk. Rheumatoid arthritis affects about . million people in the United States while osteoarthritis affects  million Americans aged  and older according to the American College of Rheumatology. More information The U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases has more about hip replacement http_InfoHip_Replacementdefault.asp."