 The proposed project is a single-site, prospective study of 300 OA patients aged 18-85 yrs undergoing primary TKR. The study is designed to identify factors from the pre-, intra- and postoperative phases of TKR that contribute to PPP at 6 months. Specific risk factors were selected because they are potentially modifiable, and therefore may be amenable to intervention. Patients will be assessed from pre-surgery to 6 months post surgery. The proposed multi-factorial and prospective approach to investigating risk factors is a vital next step towards understanding the complex phenomenon of PPP. 