Accuracy of the Transpatellar Tendon Approach to Knee Arthrocentesis

The purpose of this study is: * To determine the accuracy of intraarticular placement with the transpatellar tendon approach as compared to the suprapatellar approach. Patients undergoing knee arthroscopy will be consented for study of the injection of the fluid into the joint prior to portal placement or commencement of knee replacement. Patients will be randomized to receive injections via the transpatellar tendon or superolateral approach. Using injectable contrast and fluoroscopy, the placement of injections into the knee will be evaluated for accuracy. Injection attempts with contrast fluid that uniformly coats the articular surface on sagittal and coronal radiographs will be counted as successful. A concentration of contrast fluid in extraarticular fat will be counted as a failure. Hypothesis: The rate of accuracy of intraarticular placement of the needle tip via the transpatellar tendon approach to knee aspiration is greater than that of the superolateral approach. * To determine the distribution of contrast material with the transpatellar tendon and superolateral apporaches. Using a previously described evaluation technique of dividing the knee into seven compartments, sagittal and coronal fluoroscopy images will be evaluated to determine the distribution of contrast fluid. Hypothesis: Contrast injected into the knee via the trasnpatellar tendon approach will penetrate as many compartments of the knee as contrast injected via the superolateral approach.