5Objective:To evaluate the values of spiral CT arthrography with multiplanar reconstruction and virtual arthroscopy technique in diagnosis of internal derangements of the knee. Methods:Ten bovine knees were used for experiment. The menisci, anterior and posterior cruciate ligaments and cartilage of these 10 bovine knees were injured with a hook. Each of the joints was injected with 100 mi air, then soon scanned with a PQ6000 spiral computed tomography scanner. The data obtained was input into the work station, and multiplanar reconstruction technique was used to illustrate lesions in the knees. The results of CT diagnosis were compared to those found by gross inspection of the specimens. Clinically, 10 knees of 9 patients diagnosed as internal derangement were evaluated with the same method after 50-70 ml air was injected into each of the joints. Nine months later, the data of 2 patients were used for CT endoscopy reconstruction. The results were compared with intraoperative findings. Results:Experimentally,the sensitivity and specificity were 88.9％ and 93.9％ by detection of meniscal abnormalities, 85.7％ and 100％ by detection of cruciate ligament lesions, and 72.7％ and 100％ by detection of cartilage damage, respectively. Clinically, the sensitivity and specificity were 90. 0％ and 95.0％ by detection of meulscal lesion. As to ligament, the figures were 85.7％ and 100％ respectively. Images of virtual arthroscopy simulated the images of real arthroscopy. Conclnsious:Spiral CT arthrography of multiplanar reconstruction technique offers fime images of internal structures of the knee, with clear border and internal structure. It is an accurate method for detecting meulscal, cruciate and collateral ligament and cartilaginous lesions that cause internal derangement of the knee.Virtual arthroscopy technique is a hopeful method for detecting reasons of derangement of the knee.