The purpose of this study is to analyze the causative factors that affect the recurrence and positive culture results of pyogenic knee arthritis after arthroscopic treatment.

A total of 69 patients, who were followed-up for more than one year after arthroscopid lavage and debridement for pyogenic knee arthritis, between February 2011 and February 2015, were retrospectively reviewed for analysis. We analyzed the factors affecting the recurrence rate, preoperative C-reactive protein (CRP) level, neutrophil count in synovial fluid, growth of bacteria in culture, and normalization of CRP level, and also analyzed potential factors that may influence the treatment results and recurrence.

The recurrence rate was significantly higher in the culture-positive group (p=0.014). Culture-positive patients had low preoperative CRP (p=0.004), shorter duration for normalization of CRP (p=0.037), shorter duration of hospital stay (p=0.001) and intravenous antibiotics use (p=0.021). The duration for normalization of the CRP level had was associated with symptom-to-treatment interval (p=0.005), neutrophil count in synovial fluid (p=0.007), and growth of bacteria in the culture (p=0.001). There were 16 cases (23.2%) culture-positive cases and 15 cases (21.7%) recurrent cases.

According to our study, early diagnosis and management affect rapid recovery of the CRP level in pyogenic arthritis of the knee. Preoperative CRP and leukocyte counts in the joint fluid are of diagnostic value in acute infection. However, it should not be overlooked that their diagnostic value is limited as a single factor as they may have low preoperative values. Therefore preoperative CRP and leukocyte counts in the joint fluid should be considered in conjunction with symptoms and intra-articular fluid manifestations. Bacteria growth in the culture are meaningful factors in an evaluation for postoperative recovery and recurrence.