Evaluation of the Medial Parapatellar Knee Injection Technique

Study Summary

The goal of our study is to present important anatomic considerations which should be considered before knee injection is performed. Additionally, we have developed important procedural augments to the traditional para-patellar injection techniques in order to exceed the accuracy and safety previously reported for the infra-patellar approaches We have developed an injection technique which mechanically is similar to current techniques practiced and poses no additional risks or discomfort to the patient. The basis of our technique and its success is through recognition of anatomic factors and avoidance of possible iatrogenic injuries which exist when using other knee injection technique. The focus of our study is to validate the clinical accuracy we have been obtaining using our technique through fluoroscopically confirmed visualized confirmation of repeated intra-articular deposit. Additionally we want to document the range of needle length we require to properly access the knee joint in our population to substantiate the importance of needle length. Needle length is a critical factor in obese patients whom have larger infra-patellar fat pads. Our hypothesis is that when using a 6 inch 22 gage needle for intra-articular knee injections through the medial joint line approach, while utilizing the medial wall of the lateral femoral condyle as an intra-articular stop point for needle insertion, the accuracy of intra-articular deposit will exceed the values currently reported in the literature which is approximately 75% success rate. To prove this point we will be injecting 2 cc of radiocontrast dye into the joint space and than immediatly view the joint flouroscopicly after the knee has been brought through 10 cycles of flexion and extension.