Septic arthritis is rarely seen in transplant patients and differs from the general population with regards to gram negative and/or atypical agents being the prominent causes. In renal transplant patients, osteonecrosis is one of the major musculo-skeletal complications. In transplant patients, immunosupressive drugs, delayed graft function, genetics, HD duration before transplantation, cause of renal failure are among the risk factors for ostenecrosis. In this case report, we present a renal transplant patient with bilateral knee osteonecrosis and septic arthritis due to Escherichia coli.