(i) Investigation of the painful knee arthroplasty

Both total and unicompartmental knee arthroplasty are effective operations for the treatment of gonarthrosis. However, up to 20% of patients will return with pain and a suboptimal functional outcome. The investigation of such a patient is critical in determining an accurate diagnosis and establishing an effective management plan. Causes of pain can be broadly classified into extrinsic and intrinsic. The commonest intrinsic causes of pain are infection, component loosening, component mal-orientation and soft tissue impingement. Extrinsic causes, including hip and spinal pathology, may be responsible for the patient’s symptoms and must be considered. Accurate evaluation uses a four-step procedure involving a detailed history, thorough clinical examination and microbiological plus imaging analysis. This review article will focus on each of these key steps and highlight some of the latest modes of investigating the painful knee arthroplasty.