Towards an understanding of the painful total knee: what is the role of patient biology?

Total knee arthroplasty (TKA) remains the treatment of choice for end-stage osteoarthritis of the knee. With an aging population, the demand for TKA continues to increase, placing a significant burden on a health care system that must function with limited resources. Although generally accepted as a successful procedure, 15-30 % of patients report persistent pain following TKA. Classically, pain generators have been divided into intra-articular and extra-articular causes. However, there remains a significant subset of patients for whom pain remains unexplained. Recent studies have questioned the role of biology (inflammation) in the persistence of pain following TKA. This article aims to serve as a review of previously identified causes of knee pain following TKA, as well as to explore the potential role of biology as a predictor of pain following knee replacement surgery.