Authors: Jennifer L. Johansson, MS Delsey M. Sherrill, MS Patrick O. Riley, PhD Paolo, Bonato, PhD Hugh Herr, PhD Affiliations: From the Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, Massachusetts (JLJ, DMS, PB, HH); The Media Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts (HH); The Harvard- MIT Division of Health Sciences and Technology, Cambridge, Massachusetts (PB, HH); and the Department of Physical Medicine and Rehabilitation, University of Virginia, Charlottesville, VA (PR). Correspondence: All correspondence and requests for reprints should be addressed to: Hugh Herr, PhD, The Media Laboratory, Massachusetts Institute of Technology, 20 Ames Street, Room 419, Cambridge, MA 02139. Disclosures: Editor’s Note: Accepted for publication June 9, 2005. Disclosures: Dr Herr received support from the Schaffer Foundation and O ¨ ssur Inc. during the period of performance of the study. Dr Herr is one of many inventors on two U.S. patents that cover the technology utilized by the O ¨ ssur Rheo prosthetic device. The patents are owned by the Massachusetts Institute of Technology. 0894-9115/05/8408-0001/0 American Journal of Physical Medicine & Rehabilitation Copyright © 2005 by Lippincott Williams & Wilkins DOI: 10.1097/01.phm.0000174665.74933.0b A Clinical Comparison of Variable- Damping and Mechanically Passive Prosthetic Knee Devices ABSTRACT Johansson JL, Sherrill DM, Riley PO, Bonato P, Herr H: A clinical comparison of variable- damping and mechanically passive prosthetic knee devices. Am J Phys Med Rehabil 2005; 84:000 – 000. Objective: Although variable-damping knee prostheses offer some im- provements over mechanically passive prostheses to transfemoral ampu- tees, there is insufficient evidence that such prostheses provide advan- tages at self-selected walking speeds. In this investigation, we address this question by comparing two variable-damping knees, the hydraulic-based Otto Bock C-leg and the magnetorheological-based O ¨ ssur Rheo, with the mechanically passive, hydraulic-based Mauch SNS. Design: For each prosthesis, metabolic data were collected on eight unilateral amputees walking at self-selected speeds across an indoor track. Furthermore, kinetic, kinematic, and electromyographic data were collected while walking at self-selected speeds across a 10-m walkway in a laboratory. Results: When using the Rheo, metabolic rate decreases by 5% compared with the Mauch and by 3% compared with the C-leg. Further- more, for the C-leg and Rheo knee devices, we observe biomechanical advantages over the mechanically passive Mauch. These advantages include an enhanced smoothness of gait, a decrease in hip work produc- tion, a lower peak hip flexion moment at terminal stance, and a reduction in peak hip power generation at toe-off. Conclusion: The results of this study indicate that variable-damping knee prostheses offer advantages over mechanically passive designs for unilateral transfemoral amputees walking at self-selected ambulatory speeds, and the results further suggest that a magnetorheological-based system may have advantages over hydraulic-based designs. balt5/z79-phm/z79-phm/z7900805/z792838-05a wilkerss S6 6/23/05 14:51 Art: PHM167643 Input-nlm August 2005 Variable-Damping vs. Mechanically Passive Prosthetic Knees 1 AQ: 1 RESEARCH ARTICLE Rapid Communication