title: Energy recovery in individuals with knee osteoarthritis.
abstract: OBJECTIVE
  Pathological gaits have been shown to limit transfer between potential (PE) and kinetic (KE) energy during walking, which can increase locomotor costs. The purpose of this study was to examine whether energy exchange would be limited in people with knee osteoarthritis (OA).
  
  
  METHODS
  Ground reaction forces during walking were collected from 93 subjects with symptomatic knee OA (self-selected and fast speeds) and 13 healthy controls (self-selected speed) and used to calculate their center of mass (COM) movements, PE and KE relationships, and energy recovery during a stride. Correlations and linear regressions examined the impact of energy fluctuation phase and amplitude, walking velocity, body mass, self-reported pain, and radiographic severity on recovery. Paired t-tests were run to compare energy recovery between cohorts.
  
  
  RESULTS
  Symptomatic knee OA subjects displayed lower energetic recovery during self-selected walking speeds than healthy controls (P = 0.0018). PE and KE phase relationships explained the majority (66%) of variance in recovery. Recovery had a complex relationship with velocity and its change across speeds was significantly influenced by the self-selected walking speed of each subject. Neither radiographic OA scores nor subject self-reported measures demonstrated any relationship with energy recovery.
  
  
  CONCLUSIONS
  Knee OA reduces effective exchange of PE and KE, potentially increasing the muscular work required to control movements of the COM. Gait retraining may return subjects to more normal patterns of energy exchange and allow them to reduce fatigue.
authors.affiliation: Michael W. Krzyzewski Human Performance Research Laboratory, DUMC 3435 Duke University Medical Center, Durham, NC 27710, USA; Department of Orthopedic Surgery, Duke University Medical Center Box 3956, Durham NC 27710, USA. Electronic address: tlsparling@me.com.
authors.forename: T L
authors.initials: TL
authors.lastname: Sparling
authors.affiliation: Department of Evolutionary Anthropology, Duke University, Durham, NC, USA. Electronic address: Daniel.schmitt@duke.edu.
authors.forename: D
authors.initials: D
authors.lastname: Schmitt
authors.affiliation: Department of Evolutionary Anthropology, Duke University, Durham, NC, USA. Electronic address: charlotte.miller@duke.edu.
authors.forename: C E
authors.initials: CE
authors.lastname: Miller
authors.affiliation: Department of Orthopedic Surgery, Duke University Medical Center Box 3956, Durham NC 27710, USA; Department of Biomedical Engineering, Duke University, Durham, NC, USA. Electronic address: farshid.guilak@duke.edu.
authors.forename: F
authors.initials: F
authors.lastname: Guilak
authors.affiliation: Duke Pain Prevention and Treatment Research Program, Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA. Electronic address: tamara.somers@dm.duke.edu.
authors.forename: T J
authors.initials: TJ
authors.lastname: Somers
authors.affiliation: Duke Pain Prevention and Treatment Research Program, Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA. Electronic address: francis.keefe@dm.duke.edu.
authors.forename: F J
authors.initials: FJ
authors.lastname: Keefe
authors.affiliation: Michael W. Krzyzewski Human Performance Research Laboratory, DUMC 3435 Duke University Medical Center, Durham, NC 27710, USA; Department of Orthopedic Surgery, Duke University Medical Center Box 3956, Durham NC 27710, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Queen
mesh_terms: D000054:Acceleration; D000368:Aged; D000886:Anthropometry; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D016022:Case-Control Studies; D004185:Disability Evaluation; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005684:Gait; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000534:rehabilitation; D010147:Pain Measurement; D011379:Prognosis; D012016:Reference Values; D012720:Severity of Illness Index; D013997:Time Factors; D016138:Walking / Q000502:physiology*
keywords: Energy recovery; Knee osteoarthritis; Locomotor costs; Mechanical work
references.citation: Acta Physiol (Oxf). 2006 Feb;186(2):127-39
references.pmid: 16497190
references.citation: Clin Orthop Relat Res. 1987 Jan;(214):278-84
references.pmid: 3791753
references.citation: Disabil Rehabil. 1997 Feb;19(2):47-55
references.pmid: 9058029
references.citation: Age Ageing. 1997 Jan;26(1):15-9
references.pmid: 9143432
references.citation: Gait Posture. 2003 Oct;18(2):47-55
references.pmid: 14654207
references.citation: J Appl Physiol Respir Environ Exerc Physiol. 1983 Aug;55(2):607-13
references.pmid: 6618953
references.citation: Exerc Sport Sci Rev. 2005 Apr;33(2):88-97
references.pmid: 15821430
references.citation: Arthritis Rheum. 1983 Aug;26(8):1017-22
references.pmid: 6603848
references.citation: J Gerontol A Biol Sci Med Sci. 2012 Oct;67(10):1114-20
references.pmid: 22451469
references.citation: Clin Orthop Relat Res. 1977 Jul-Aug;(126):246-55
references.pmid: 598127
references.citation: Arthritis Rheum. 2008 Jan;58(1):26-35
references.pmid: 18163497
references.citation: J Exp Biol. 2012 May 15;215(Pt 10):1728-39
references.pmid: 22539740
references.citation: Osteoarthritis Cartilage. 2005 Mar;13(3):206-10
references.pmid: 15727886
references.citation: J Appl Physiol (1985). 2005 Feb;98(2):579-83
references.pmid: 15649878
references.citation: J Physiol. 1977 Jun;268(2):467--81
references.pmid: 874922
references.citation: Am J Phys Med. 1985 Apr;64(2):57-70
references.pmid: 3993758
references.citation: Arthritis Rheum. 2004 Apr;50(4):1172-8
references.pmid: 15077299
references.citation: Am J Physiol. 1977 Nov;233(5):R243-61
references.pmid: 411381
references.citation: J Biomech. 2004 Jun;37(6):817-25
references.pmid: 15111069
references.citation: J Rheumatol. 1988 Dec;15(12):1833-40
references.pmid: 3068365
references.citation: Ann Rheum Dis. 1957 Dec;16(4):494-502
references.pmid: 13498604
references.citation: Arch Phys Med Rehabil. 2009 Nov;90(11):1874-9
references.pmid: 19887211
references.citation: Ann Rheum Dis. 1991 Jan;50(1):8-13
references.pmid: 1994877
references.citation: Hum Mov Sci. 2007 Aug;26(4):617-56
references.pmid: 17617481
references.citation: Aging Clin Exp Res. 2009 Dec;21(6):463-9
references.pmid: 20154517
references.citation: J Orthop Res. 2002 Jan;20(1):101-7
references.pmid: 11853076
references.citation: J Exp Biol. 2004 Jan;207(Pt 3):399-410
references.pmid: 14691087
references.citation: Pain. 2012 Jun;153(6):1199-1209
references.pmid: 22503223
references.citation: J Physiol. 1976 Nov;262(3):639-57
references.pmid: 1011078
references.citation: J Electromyogr Kinesiol. 1999 Apr;9(2):149-57
references.pmid: 10098715
references.citation: Am J Phys Med Rehabil. 1996 Sep-Oct;75(5):375-9
references.pmid: 8873706
references.citation: J Biomech. 1987;20(10):987-95
references.pmid: 3693380
references.citation: Arch Phys Med Rehabil. 2005 Nov;86(11):2189-94
references.pmid: 16271569
references.citation: J Women Aging. 2009;21(3):159-70
references.pmid: 20183142