The purpose of this study is to determine whether an undirected synovial biopsy technique has the same accuracy in detecting periprosthetic joint infection in the knee as an arthroscopic assisted directed synovial biopsy technique.

Successful treatment of an infected joint arthroplasty depends on correctly identifying the responsible pathogens. The value of a preoperative biopsy remains controversial. We compared the sensitivity and specificity of two techniques of synovial biopsy of knee joint arthroplasties suspicious for infection and asked whether the results correlate with intraoperative findings at revision.

Inclusion Criteria:

• Chronic painful knee prosthesis planned for synovial biopsy to detect infection
• Culture-negative joint aspiration

Exclusion Criteria:

• Co-morbidities: Tumour disease, immune suppression