Falls Associated with Muscle Strength in Patients with Knee Osteoarthritis and Self-reported Knee Instability.
OBJECTIVE
We aimed to evaluate the associations between knee muscle strength (MS) and falls, controlling for knee joint proprioception, varus-valgus knee joint laxity, and knee pain, among patients with knee osteoarthritis (OA) reporting knee instability.


METHODS
A sample of 301 subjects (203 women, 98 men, 35-82 yrs) with established knee OA and self-reported knee instability was studied. The occurrence of at least 1 fall in the previous 3 months was assessed by questionnaire. Maximum knee extension and flexion strength were measured isokinetically. Additionally, proprioception, varus-valgus laxity, and pain were assessed. Student t tests were used to assess differences between subgroups. The association of muscle strength and falls was calculated using univariate and multivariate logistic regression analysis.


RESULTS
Over 10% of the subjects (31 out of 301) reported a fall in the previous 3 months. High knee extension muscle strength (crude OR 0.3, 95% CI 0.1-0.8, p = 0.022) and high knee flexion muscle strength (crude OR 0.2, 95% CI 0.0-1.0, p = 0.048) were associated with a lower risk of falls. Proprioception and laxity did not confound this relationship. After adjusting for pain, extensor strength had an adjusted OR of 0.5 (95% CI 0.2-1.4, p = 0.212) for falls and flexor strength had an adjusted OR of 0.4 (95% CI 0.1-2.3, p = 0.312).


CONCLUSIONS
High knee extension and flexion muscle strength decreased the risk of falls in patients with knee OA and self-reported knee instability. After considering the effect of pain, there was insufficient statistical power to detect an association between muscle strength and falls, which might be because of the low number of subjects who fell (n = 31).
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University. a.d.zwart@reade.nl.
Arjan H
AH
de Zwart
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Martin
M
van der Esch
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Mirjam A G M
MA
Pijnappels
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Marco J M
MJ
Hoozemans
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Marike
M
van der Leeden
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Leo D
LD
Roorda
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Joost
J
Dekker
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Willem F
WF
Lems
From the Amsterdam Rehabilitation Research Center/Reade; MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; Department of Rehabilitation Medicine, and Department of Psychiatry, and Department of Rheumatology, VU University Medical Center; Jan van Breemen Research Institute/Reade, Amsterdam, the Netherlands; King Abdulaziz University, Jeddah, Saudi Arabia.A.H. de Zwart, MSc, Amsterdam Rehabilitation Research Center/Reade; M. Pijnappels, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Esch, PhD, Amsterdam Rehabilitation Research Center/Reade; M.J. Hoozemans, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam; M. van der Leeden, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine, VU University Medical Center; L.D. Roorda, MD, PT, PhD, Amsterdam Rehabilitation Research Center/Reade; J. Dekker, PhD, Amsterdam Rehabilitation Research Center/Reade, and Department of Rehabilitation Medicine and Department of Psychiatry, VU University Medical Center; W.F. Lems, MD, PhD, Department of Rheumatology, VU University Medical Center, and Jan van Breemen Research Institute/Reade; J.H. van Dieën, PhD, MOVE Research Institute Amsterdam, Faculty of Human Movement Sciences, VU University Amsterdam, and King Abdulaziz University.
Jaap H
JH
van Dieën
D000058:Accidental Falls; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000150:complications / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D011434:Proprioception / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology
ACCIDENTAL FALLS; JOINT LAXITY; KNEE JOINT; MUSCLE STRENGTH; OSTEOARTHRITIS; PROPRIOCEPTION