Dynamic electromyography after cruciate-retaining total knee arthroplasty revealed a threefold quadriceps demand compared with the contralateral normal knee.

Quadriceps functional impairment accounts for a considerable amount of morbidity after knee replacement. Cruciate-retaining total knee arthroplasty (CR-TKA) may predispose to increased quadriceps demand. We compared bilateral relative quadriceps effort in seven patients with successful unilateral CR-TKA at least 2years after surgery. Dynamic electromyography (EMG) recorded quadriceps activity during walking recorded simultaneously with gait analysis using IDEEA. There was greater EMG activity for the operated knees, both in amplitude (43.08±26.47 vs. 16.02±5.38, P=.0355), and the area under the curve (7231.1±3869.8 vs. 2547.3±1007.9, P=.0267). The onset and duration of muscle activity were similar for both knees (P=.74). CR-TKA demonstrated threefold EMG activity and muscle effort during normal walking. The study suggested that quadriceps functional deficiency is associated with CR-TKA.