title: Response to letter to the editor regarding "Application of principal component analysis in clinical gait research".
authors.affiliation: Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology NTNU, 7489 Trondheim, Norway; Department of Physical Performance, Norwegian School of Sport Sciences, Oslo, Norway. Electronic address: peter.federolf@ntnu.no.
authors.forename: Peter
authors.initials: P
authors.lastname: Federolf
authors.affiliation: Department of Kinesiology, University of Massachusetts-Amherst, Amherst, MA, USA.
authors.forename: Katharine
authors.initials: K
authors.lastname: Boyer
authors.affiliation: Department of Mechanical Engineering, Stanford University, USA; Department of Orthopedic Surgery, Stanford University, USA; Veterans Administration, Palo Alto, CA, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Andriacchi
mesh_terms: D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D020370:Osteoarthritis, Knee / Q000503:physiopathology*