Research Article| Volume 99, 105736, October 2022

The associations of knee extensor muscle steadiness with maximal voluntary torque and physical function in patients with knee osteoarthritis


      • Low maximal voluntary torque is associated with low muscle steadiness in patients with knee osteoarthritis.
      • Muscle steadiness is not associated with physical function.
      • Maximal voluntary torque remains a reliable objective measure of physical function.



      Muscle weakness is characteristic of knee osteoarthritis. Muscle steadiness may be an important adjunct to knee muscle strength in improving physical function in knee osteoarthritis. However, the role of muscle steadiness is uncertain.


      To determine the associations of knee extensor muscle steadiness with maximal voluntary torque and physical function in patients with knee osteoarthritis.


      Baseline data from 177 patients in a randomized clinical trial were used. Isokinetic knee extension torque was processed into maximal voluntary torque [Nm]. Muscle steadiness was expressed as the coefficient of variance [%] and as peak power frequency [Hz]. Physical function was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, the Get-Up-and-Go and Stair-climb tests. Associations were determined using regression analyses and adjusted for confounders.


      Lower muscle steadiness (i.e., higher coefficient of variance and peak power frequency) was associated with lower maximal voluntary torque (B = − 7.38, [−10.8, −3.95], R2 = 0.10 and B = −14.71, [−28.29, −1.13], R2 = 0.03, respectively). Higher coefficient of variance was associated with lower self-reported physical function (B = 1.14, [0.11,2.17], R2 = 0.03) and remained significant after adjusting for potential confounders. Peak power frequency was not associated with physical function.


      Low muscle steadiness was weakly associated with low muscle strength and poorer self-reported physical function. Muscle steadiness and muscle strength seem to be different attributes of muscle function. There is no convincing evidence that muscle steadiness is an important adjunct in studying physical function in patients with knee osteoarthritis.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Clinical Biomechanics
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Baltzopoulos V.
        • Brodie D.A.
        Isokinetic dynamometry. Applications and limitations.
        Sports Med. 1989; 2: 101-116
        • Bellamy N.
        • Buchanan W.W.
        • Goldsmith C.H.
        • Campbell J.
        • Stitt L.W.
        Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee.
        J. Rheumatol. 1988; 15: 1833-1840
        • Bennell K.L.
        • Wrigley T.V.
        • Hunt M.A.
        • Lim B.W.
        • Hinman R.S.
        Update on the role of muscle in the genesis and management of knee osteoarthritis.
        Rheum. Dis. Clin. N. Am. 2013; 39: 145-176
        • Bryant A.L.
        • Pua Y.H.
        • Clark R.A.
        Morphology of knee extension torque-time curves following anterior cruciate ligament injury and reconstruction.
        J. Bone Joint Surg. Am. 2009; 91: 1424-1431
        • Christou E.A.
        Aging and variability of voluntary contractions.
        Exerc. Sport Sci. Rev. 2011; 39: 77-84
        • Christou E.A.
        • Carlton L.G.
        Old adults exhibit greater motor output variability than young adults only during rapid discrete isometric contractions.
        J. Gerontol. A Biol. Sci. Med. Sci. 2001; 56: B524-B532
        • Clark B.C.
        • Pierce J.R.
        • Manini T.M.
        • Ploutz-Snyder L.L.
        Effect of prolonged unweighting of human skeletal muscle on neuromotor force control.
        Eur. J. Appl. Physiol. 2007; 100: 53-62
        • de Zwart A.H.
        • Dekker J.
        • Roorda L.D.
        • van der Esch M.
        • Lips P.
        • van Schoor N.M.
        • Heijboer A.C.
        • Turkstra F.
        • Gerritsen M.
        • Häkkinen A.
        • Bennell K.
        • Steultjens M.P.
        • Lems W.F.
        • van der Leeden M.
        High-intensity versus low-intensity resistance training in patients with knee osteoarthritis: a randomized controlled trial.
        Clin. Rehabil. 2022; 25 (2692155211073039)
        • Dobson F.
        • Hinman R.S.
        • Hall M.
        • et al.
        Reliability and measurement error of the osteoarthritis research society international (OARSI) recommended performance-based tests of physical function in people with hip and knee osteoarthritis.
        Osteoarthr. Cartil. 2017; 25: 1792-1796
        • Enoka R.M.
        • Christou E.A.
        • Hunter S.K.
        • Kornatz K.W.
        • Semmler J.G.
        • Taylor A.M.
        • Tracy B.L.
        Mechanisms that contribute to differences in motor performance between young and old adults.
        J. Electromyogr. Kinesiol. 2003; 13: 1-12
        • Fink B.
        • Egl M.
        • Singer J.
        • Fuerst M.
        • Bubenheim M.
        • Neuen-Jacob E.
        Morphologic changes in the vastus medialis muscle in patients with osteoarthritis of the knee.
        Arthritis Rheum. 2007; 56: 3626-3633
        • Fitzgerald G.K.
        • Piva S.R.
        • Irrgang J.J.
        Reports of joint instability in knee osteoarthritis: its prevalence and relationship to physical function.
        Arthritis Rheum. 2004; 51: 941-946
        • Haefeli M.
        • Elfering A.
        Pain assessment.
        Eur. Spine J. 2006; 15: S17-S24
        • Hirokawa S.
        • Solomonow M.
        • Luo Z.
        • Lu Y.
        • D’Ambrosia R.
        Muscular co-contraction and control of knee stability.
        J. Electromyogr. Kinesiol. 1991; 1: 199-208
        • Hortobágyi T.
        • Mizelle C.
        • Beam S.
        • DeVita P.
        Old adults perform activities of daily living near their maximal capabilities.
        J. Gerontol. A Biol. Sci. Med. Sci. 2003; 58: 453-460
        • Hortobágyi T.
        • Garry J.
        • Holbert D.
        • Devita P.
        Aberrations in the control of quadriceps muscle force in patients with knee osteoarthritis.
        Arthritis Rheum. 2004; 51: 562-569
        • Hortobágyi T.
        • Westerkamp L.
        • Beam S.
        • Moody J.
        • Garry J.
        • Holbert D.
        • DeVita P.
        Altered hamstring-quadriceps muscle balance in patients with knee osteoarthritis.
        Clin Biomech (Bristol, Avon). 2005; 20: 97-104
        • Hurley M.V.
        • Scott D.L.
        • Rees J.
        • Newham D.J.
        Sensorimotor changes and functional performance in patients with knee osteoarthritis.
        Ann. Rheum. Dis. 1997; 56: 641-648
        • Jones K.E.
        • Hamilton A.F.
        • Wolpert D.M.
        Sources of signal-dependent noise during isometric force production.
        J. Neurophysiol. 2002; 88: 1533-1544
        • Kellgren J.H.
        • Lawrence J.S.
        Radiological assessment of osteo-arthrosis.
        Ann. Rheum. Dis. 1957; 16: 494-502
        • Kohn M.D.
        • Sassoon A.A.
        • Fernando N.D.
        Classifications in brief: Kellgren-Lawrence classification of osteoarthritis.
        Clin. Orthop. Relat. Res. 2016; 474: 1886-1893
        • Mau-Moeller A.
        • Jacksteit R.
        • Jackszis M.
        • Feldhege F.
        • Weippert M.
        • Mittelmeier W.
        • Bader R.
        • Skripitz R.
        • Behrens M.
        Neuromuscular function of the quadriceps muscle during isometric maximal, submaximal and submaximal fatiguing voluntary contractions in knee osteoarthrosis patients.
        PLoS One. 2017; 12e0176976
        • McConnell S.
        • Kolopack P.
        • Davis A.M.
        The Western Ontario and McMaster universities osteoarthritis index (WOMAC): a review of its utility and measurement properties.
        Arthritis Rheum. 2001; 45: 453-461
        • Palmieri-Smith R.M.
        • Thomas A.C.
        • Karvonen-Gutierrez C.
        • et al.
        Isometric quadriceps strength in women with mild, moderate, and severe knee osteoarthritis.
        Am J Phys Med Rehabil. 2010; 89: 541-548
        • Piva S.R.
        • Fitzgerald G.K.
        • Irrgang J.J.
        • Bouzubar F.
        • Starz T.W.
        Get up and go test in patients with knee osteoarthritis.
        Arch. Phys. Med. Rehabil. 2004; 85: 284-289
        • Ploutz-Snyder L.L.
        • Manini T.
        • Ploutz-Snyder R.J.
        • Wolf D.A.
        Functionally relevant thresholds of quadriceps femoris strength.
        J. Gerontol. A Biol. Sci. Med. Sci. 2002; 57: B144-B152
        • Pua Y.H.
        • Clark R.A.
        • Bryant A.L.
        Physical function in hip osteoarthritis: relationship to isometric knee extensor steadiness.
        Arch. Phys. Med. Rehabil. 2010; 91: 1110-1116
        • Pua Y.H.
        • Ong P.H.
        • Ho J.Y.
        • Bryant A.L.
        • Webster E.
        • K, Clark RA.
        Associations of isokinetic knee steadiness with hop performance in patients with ACL deficiency.
        Knee Surg. Sports Traumatol. Arthrosc. 2015; 23: 2185-2195
        • Roorda L.D.
        • Jones C.A.
        • Waltz M.
        • et al.
        Satisfactory cross cultural equivalence of the Dutch WOMAC in patients with hip osteoarthritis waiting for arthroplasty.
        Ann. Rheum. Dis. 2004; 63: 36-42
        • Roos E.M.
        • Herzog W.
        • Block J.A.
        • Bennell K.L.
        Muscle weakness, afferent sensory dysfunction and exercise in knee osteoarthritis.
        Nat. Rev. Rheumatol. 2011; 7: 57-63
        • Singh N.B.
        • Arampatzis A.
        • Duda G.
        • Heller M.O.
        • Taylor W.R.
        Effect of fatigue on force fluctuations in knee extensors in young adults.
        Philos Trans A Math Phys Eng Sci. 1920; 2010: 2783-2798
        • Slemenda C.
        • Brandt K.D.
        • Heilman D.K.
        • et al.
        Quadriceps weakness and osteoarthritis of the knee.
        Ann. Intern. Med. 1997; 127: 97-104
        • Tracy B.L.
        • Enoka R.M.
        Older adults are less steady during submaximal isometric contractions with the knee extensor muscles.
        J. Appl. Physiol. 2002; 92: 1004-1012
        • Tracy B.L.
        • Byrnes W.C.
        • Enoka R.M.
        Strength training reduces force fluctuations during anisometric contractions of the quadriceps femoris muscles in old adults.
        J. Appl. Physiol. 2004; 96: 1530-1540
        • Van der Esch M.
        • Steultjens M.
        • Harlaar J.
        • Knol D.
        • Lems W.
        • Dekker J.
        Joint laxity and the relationship between muscle strength and functional ability in patients with osteoarthritis of the knee.
        Arthritis Rheum. 2006; 55: 953-959
        • Van der Esch M.
        • Knoop J.
        • Hunter D.J.
        • et al.
        The association between reduced knee joint proprioception and medial meniscal abnormalities using MRI in knee osteoarthritis: results from the Amsterdam osteoarthritis cohort.
        Osteoarthr. Cartil. 2013; 21: 676-681
        • Williams G.N.
        • Chmielewski T.
        • Rudolph K.
        • Buchanan T.S.
        • Snyder-Mackler L.
        Dynamic knee stability: current theory and implications for clinicians and scientists.
        J Orthop Sports Phys Ther. 2001; 31: 546-566
        • Yoshitake Y.
        • Kouzaki M.
        • Fukuoka H.
        • Fukunaga T.
        • Shinohara M.
        Modulation of muscle activity and force fluctuations in the plantar flexors after bedrest depends on knee position.
        Muscle Nerve. 2007; 35: 745-755