With the increased life expectancies, total joint arthroplasties have been performed increasingly day by day on more patients. Simultaneously, the number of patients who suffered periprosthetic joint infections (PJI), which is one of the most troublesome complications of this treatment method, is also increasing. PJI can destroy the successful results of a well-performed total knee arthroplasty. Patient and surgeon satisfaction rates are decreased due to difficulties in the diagnosis and the treatment of the disease, as well as long time of recovery and higher costs. The current diagnostic tools are erythrocyte sedimentation rate, C-reactive protein, synovial white blood cell count, cultures, histological investigations, imaging and other developing methods. Treatment choices include irrigation and debridement, onestage implant exchange, two-stage exchange and use of antibiotic loaded cement spacers, and antibiotic suppression in which adequate surgical treatment cannot be performed. Treatment options are usually determined according to time of onset of the symptoms, virulence and isolation of the microorganisms, and patient specific factors. Although one-stage revisions have advantages on the rate of morbidity and functional recovery, two-stage revisions are still the golden standard and have great success rates. Successful results may be obtained with identification of the infection, radical debridement, implant exchange and appropriate antibiotic therapy. This review summarizes the current concept in the diagnosis and treatment of PJI.