Motion of the patella during walking: a video digital-fluoroscopic study in healthy volunteers.

OBJECTIVE: The alignment of the quadriceps muscle and patella suggests that the patella should deviate laterally out of the patellar groove as the quadriceps muscle contracts during walking. The surgical treatment of patellar subluxation has been based on this presumption. The purpose of this study was to determine the movements of the patella in relation to the other bones of the knee joint during normal walking. This is the first study we know of that uses radiographs to show these movements. SUBJECTS AND METHODS: Eight healthy adult volunteers with no previous complaints referable to the knee walked on a slowly moving treadmill while their patellae were imaged fluoroscopically in the anteroposterior plane with a Toshiba C-arm. Images were retrieved, transferred to radiographic film, and randomized to prevent the observers from knowing the order of images. The position of the patella was measured and plotted in relation to fixed points of the knee. RESULTS: In each of the subjects at every gait cycle, the patella was observed to move vertically first, followed by a sudden shift to the medial side before returning to its original position. CONCLUSION: Contrary to conventional understanding, our results show that the patella deviates medially rather than laterally during walking. This occurs because of differential contraction of the components of the quadriceps muscle during walking. The management of painful and subluxated patellae must be reevaluated in light of this finding.