A bacterial infection of an artificial joint is a serious complication that often requires additional surgery to exchange the arthroplasty. It is also difficult to recognize an infected joint, as the symptoms caused by the infection are very similar to those of other problems with arthroplasties, such as loosening of the implant. To improve the ability to diagnose prosthetic joint infections, this study compares the levels of calprotectin, a specific inflammatory protein, in the joint fluid of infected joints and joints with other complications. The underlying hypothesis is that the level of calprotectin in infected joints is significantly higher, thus facilitating the diagnosis of prosthetic joint infection.

Inclusion Criteria:

• scheduled arthroplasty exchange for any of the following reasons:
• infection
• loosening
• instability
• malalignment
• periprosthetic fracture

Exclusion Criteria:

• acute prosthetic joint infection

Patients with painful or failed arthroplasty of the hip or knee joint scheduled for partial or complete arthroplasty exchange.