Objective:To evaluate the values of spiral CT arthrography with multiplanar reconstruction and virtual arthroscopy technique i n 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 kne es were injured with a hook. Each of the joints was injected with 100 ml air, th en soon scanned with a PQ6000 spiral computed tomography scanner. The data obtai ned was input into the work station, and multiplanar reconstruction technique wa s used to illustrate lesions in the knees. The results of CT diagnosis were comp ared to those found by gross inspection of the specimens. Clinically, 10 knees o f 9 patients diagnosed as internal derangement were evaluated with the same meth od 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 we re compared with intraoperative findings. Results:Experimentally, the sensitivity and specificity were 88.9 % and 93.9 % by detection of meniscal abnormalities, 85.7 % and 10 0% by detection of cruciate ligament lesions, and 72.7 % and 100% by detectio n of cartilage damage, respectively. Clinically, the sensitivity and specificity were 90.0 % and 95.0 % by detection of meniscal lesion. As to ligament, t he figures were 85.7 % and 100% respectively. Images of virtual arthroscopy s imulated the images of real arthroscopy. Conclusions:Spiral CT arthrography of multiplanar reconstructi on technique offers fine images of internal structures of the knee, with clear b order and internal structure. It is an accurate method for detecting meniscal, cruciate and collateral ligament and cartilaginous lesions that cause internal d erangement of the knee. Virtual arthroscopy technique is a hopeful method for de tecting reasons of derangement of the knee. Objective: 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 kne es were injured with a hook. Each of the joints was injected with 100 ml air, th en soon scanned with a PQ6000 spiral computed tomography scanner. The data obtai ned was input into the work station, and multiplanar reconstruction techniques wa s used to The results of CT diagnosis were comp wered to those found by gross inspection of the specimens. Clinically, 10 knees of 9 patients diagnosed as internal derangement were evaluated with the same meth od 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 we re compared with intraoperative 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 detectio n of cartilage damage, respectively. As of ligament, he figures were 85.7% and 100% respectively. Images of virtual arthroscopy s imulated the images of real arthroscopy. Conclusions: Spiral CT arthrography of multiplanar reconstructi on technique offers fine images of internal structures of the knee, with clear b order and internal structure. It is an accurate method for detecting meniscal, cruciate and collateral ligament and cartilaginous lesions that cause internal d erangement of the knee. Virtual arthroscopy technique is a hopeful method for de tecting reasons of derangement of the knee.