The value of colour Doppler sonography of the knee joint: a useful tool to discriminate inflammatory from non-inflammatory disease?

OBJECTIVE: To determine the diagnostic value of colour Doppler ultrasound (CDUS) in patients with inflammatory arthritis (IA) vs non-inflammatory disease (e.g. OA) of the knee joint. METHODS: Standardized CDUS examinations were performed in 111 knee joints of 106 patients (70 women and 36 men) presenting with severe OA (n = 72) or confirmed IA (n = 39) of one or both knee joints to determine the degree of synovial inflammation in a semiquantitative fashion. To definitely distinguish inflammatory from non-inflammatory disease, SF was obtained from every patient within 24 h after sonography and analysed SFs containing ≤1000 white blood cells (WBC)/µl were considered non-inflammatory, whereas ≥5000 WBC/µl were classified as inflammatory. RESULTS: The CDUS sum score of OA patients was determined to be 3.3 (range 0-8). In contrast, IA patients exhibited significantly elevated synovitis score of 5.3 (range 3-9) (P < 0.001). However, high synovial CDUS activity could be observed in OA patients sporadically. Therefore, there is no definitive CDUS threshold that clearly separates OA from IA patients. CONCLUSION: CDUS is a valuable instrument to assist clinicians in distinguishing OA from IA of the knee joint, but nevertheless should always be interpreted within the clinical context.