 In the early phase after a total knee arthroplasty TKA, patients experience multi-level weakness in the operated leg, which is caused primarily by reduced central nervous system CNS activation failure of the muscles - especially the knee extensors. This considerable loss of muscle strength relates to reduced functional performance. Early-commenced, progressive strength training of the knee extensors of the operated leg therefore seems rational. However, the concern is that this type of early-commenced, intense physical rehabilitation exacerbates post-operative symptoms, such as knee joint pain. 