• Doris Vahtrik, Helena Gapeyeva, Herje Aibast, Jaan Ereline, Tatjana Kums, Tiit Haviko, Aare Märtson, Galina Schneider, and Mati Pääsuke.
• Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014, Tartu, Estonia. Doris.Vahtrik@ut.ee
• Knee Surg Sports Traumatol Arthrosc. 2012 Oct 1;20(10):2017-25.

PurposeThe aim of the present study was to evaluate an isometric voluntary force generation and relaxation capacity of the quadriceps femoris (QF) muscle prior and after total knee arthroplasty (TKA).MethodsIsometric maximal voluntary contraction force, rate of force development, voluntary activation, half-relaxation time, and latency of contraction of the QF muscle were recorded in 12 female patients (aged 49-68 years) with knee osteoarthritis one day before, 3 and 6 months following TKA in the operated and nonoperated leg. Knee pain intensity was assessed by visual analog scale, and Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire was used to assess knee problems during daily living.ResultsA significant decrease in knee pain and significant increase in KOOS were established after TKA. Maximal voluntary isometric force in the operated leg was lower (P < 0.05) before, 3 and 6 months after TKA as compared to the nonoperated leg. Rate of force development of the QF muscle in the operated leg compared to the nonoperated leg was significantly lower (P < 0.05) 3 and 6 months after TKA. Voluntary activation, latency of contraction, and half-relaxation time of the QF muscle did not differ significantly before, 3 and 6 months after TKA.ConclusionsThe present study indicated reduced maximal and explosive strength of quadriceps femoris muscle in the operated leg 3 and 6 months after TKA with no significant changes in voluntary activation, and capacity for rapid contraction and relaxation.Level Of EvidenceProspective comparative study, Level II.

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