Voluntary activation and decreased force production of the quadriceps femoris muscle after total knee arthroplasty

Background and Purpose. Quadriceps femoris muscle weakness as manifested by a decrease in force-generating capability. is a persistent. problem after total knee arthroplasty (TKA). The authors hypothesized that (1) Patients with a TKA would have decreased quadriceps femoris muscle performance (weakness) and impaired volitional Activation when compared with a group of older adults without knee pathology, (2) pain and age would account for a large. portion of the variability in Volitional activation After surgery, and (3) volitional activation in the TKA group would account for a large portion of the variability in force production. Subjects. Comparison subjects were 52 volunteer's (mean age = 72.2 years, SD=5.34, range=64-85). The TKA group comprised 52 patients (mean age=64.9 Years, SD=7.72, range=49-78) with a diagnosis of osteoarthritis who had undergone a tricompartmental, cemented TKA. Methods. Knee extension force was' measured using a burst superimposition technique, where a supramaximal burst of electrical stimulation was superimposed on a maximal voluntary isometric contraction (MVIC). The amount of failure of volitional. activation is determined by the amount of electrical augmentation of force beyond a person's MVIC at the instant of the application of the electrical burst. Results. The average normalized knee extension force of the TKA group was 64% lower than that of the comparison group. The average volitional activation deficit in the TKA group (26%) was 4 times as great as the comparison group's deficit (6%). Age did not correlate with quadriceps, I femoris muscle activation, and knee pain explained only a small portion of the variance in knee extension force (r(2) = .17). Volitional activation was highly correlated with knee extension force production (r(2) = .65)., Discussion and Conclusion. Considerable quadriceps femoris muscle. inhibition After surgery has several, implications for recovery. Rehabilitation programs, that focus on volitional exercise alone are p unlikely to overcome this pronounced failure of activation. Early interventions focused at improving quadriceps femoris muscle voluntary activation may improve efforts. to restore muscle force.