Impaired postural balance in the morning in patients with knee osteoarthritis.
Postural balance (PB) is frequently used as an outcome measure in clinical and research settings when assessing patients with knee osteoarthritis (OA). Pain and stiffness is known to affect PB, and is elevated in the morning and evening in OA patients. The aim of this study was to explore if time-of-day affects PB control in knee OA patients. Centre Of Pressure (COP) excursion was measured (100Hz) by force plate technique at selected time-points (9.00 a.m., 12.30 p.m. and 4.00 p.m.) during a single day in 32 knee OA patients aged 66.0 (10.3) years. A rigorous protocol was followed to ensure comparable testing conditions across time-points. PB control was quantified by the COP variables: velocity moment (mm(2)/s), total sway area (mm(2)), total sway length (mm) and confidence ellipse area (mm(2)). A two-way mixed-effects model showed that PB significantly improved between 9.00 a.m. and 12.30 p.m. in three out of four COP variables. The observed improvement was 11.9% (p=0.011) for velocity moment, 12.2% (p=0.011) for total sway area and 9.4% (p<0.001) for total sway length. PB appears to be impaired in the morning relative to midday in knee OA patients. Thus, it is recommended that time of assessment is standardized between sessions when assessing PB in clinical and research settings in knee OA patients.
Orthopaedic Surgery Research Unit, Aalborg University Hospital, Denmark. Electronic address: rasmussoerensen@msn.com.
Rasmus Reinholdt
RR
Sørensen
Department of Geriatrics, Aalborg University Hospital, Denmark.
Martin Grønbech
MG
Jørgensen
Orthopaedic Surgery Research Unit, Aalborg University Hospital, Denmark.
Sten
S
Rasmussen
Orthopaedic Surgery Research Unit, Aalborg University Hospital, Denmark; Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
Søren Thorgaard
ST
Skou
D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D004856:Postural Balance / Q000502:physiology*; D012678:Sensation Disorders / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D064232:Visual Analog Scale
Centre of pressure; Force plate analysis; Knee osteoarthritis; Postural balance; Time-of-day