[The Berlin diagnostic algorithm for painful knee TKA]

Approximately 20% of patients are unsatisfied with their postoperative results after total knee arthroplasty (TKA). Main causes for revision surgery are periprosthetic infection, aseptic loosing, instability and malalignment. In rare cases secondary progression of osteoarthritis of the patella, periprosthetic fractures, extensor mechanism insufficiency, polyethylene wear and arthrofibrosis can cause the necessity for a reintervention. Identifying the reason for a painful knee arthroplasty can be very difficult, but is a prerequisite for a successful therapy.

The aim of this article is to provide an efficient analysis of the painful TKA by using a reproducible algorithm.

Basic building blocks are the medical history with the core issues of pain character and the time curve of pain concerning surgery. This is followed by the basic diagnostics, including clinical, radiological, and infectiological investigations. Unique failures like periprosthetic infection or aseptic loosening can thereby be diagnosed in the majority of cases. If the cause of pain is not clearly attributable using the basic diagnostics tool, further infectiological investigation or diagnostic imaging are necessary. If the findings are inconsistent, uncommon causes of symptoms, such as extra-articular pathologies, causalgia or arthrofibrosis, have to be considered. In cases of ongoing unexplained pain, a revision is not indicated. These patients should be re-evaluated after a period of time.