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.

PEMF therapy is the use of electromagnetic fields in a pulsating pattern directed towards the body.

The clinical use of PEMF therapies in orthopedics has been approved for over 40 years and commonly entail analgesic benefits. When specifically targeting the knee, however, evidence that the technology improves pain, physical function, and quality of life has been inconclusive, probably due to the unaddressed muscle weakness. Therefore, the approach employed in the present study was to target the leg musculature for its delivery of regenerative agents that naturally promote healing. The therapy entails a muscle-targeted, low-energy PEMF therapy previously used in human trials. Notably, this same PEMF paradigm was shown to improve functional mobility, increase lean muscle mass, and reduce pain in a community cohort containing frail elderly subjects. This PEMF paradigm has been demonstrated effective in promoting human muscle regeneration by inducing mitochondrial adaptations, similar to those invoked during oxidative muscle development in response to exercise

Inclusion Criteria:

- subjects with knee osteoarthritis will be included:

1. radiographic Kellgren/Lawrence scale knee OA grade ≥3
2. enlistment on a TKR surgical waiting list; ability to comply with the trial assessments and fully comprehend questionnaires;
3. be over 50 years of age and
4. ability to walk unaided over 6 meters.

Exclusion Criteria:

• 1. With medical or musculoskeletal problems that could affect the ability to complete assessments (i.e. with walking aids or wheel-chaired).

  2. Severe cognitive impairments and neurological disorders that will affect data collection by questionnaires.

  3. Any medical conditions which are contraindicated to do exercise by PARQ restricting any physical activity.

  4. history of knee or hip surgeries 5. body mass index over 30 kg/m2 and 6. history of cancer.

starting 6 months after publication

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It is doubled blinded, a subject 's specific ID card will be provided for each of the enrolled subject and the investigators don't know whether it is PEMF or Sham treatment for that subject's specific ID card. And the investigator will ask the manufactory about the number of grouping at the end of the study.