A double-blinded, randomizepd controlled trial to investigate the treatment effects of pulsed electromagnetic field (PEMF) on end stage of knee osteoarthritis patients with sarcopenia will be carried out. Subjects will be recruited from the Prince of Wales Hospital. Sixty participants age ≥ 60 will be invited to join this trial after informed consent. They will be randomised to any of the 2 groups: intervention group (n=30; PEMF (Quantum Tx) treatment), and control group (n=30; sham treatment with dummy exposure to PEMF). Both group will receive home-based exercise. Baseline measurements include appendicular muscle mass by DXA, bone microarchitecture (XtremeCT II), knee flexion and extension strength by handheld dynamometer, knee flexion and extension range of motion by goniometer, self-reported knee pain (VAS) and function by The Knee Injury and Osteoarthritis Outcome Score (KOOS), International Physical Activity Questionnaire (IPAQ) for assessment of physical activity level, quality of life by SF-36, hand grip test, bioelectrical impedance analysis （BIA）of body composition, postural stability, chair stand test, 30s arm curl test and 6-meter walking test. These measurements will be performed again at middle and end of treatment, 3, 6, and 12 months after commencement of treatment, except DXA, which will not be performed at the midpoint. In addition, blood samples will be taken at baseline, middle, and end of treatment, 3, 6, and 12 months after commencement of treatment, for determing of serum myokines which are reported to be sensitive to PEMF treatment and contribute to myogenesis. The aim of this study is to conduct a double-blinded, randomized controlled trial to investigate the effects of PEMF treatment on muscle gain and pain relief in knee osteoarthritis with sarcopenia elderly in Hong Kong. We hypothesize that PEMF treatment is effective to promote a gain in muscle mass and function and pain relief in knee osteoarthritis with sarcopenia elderlies.