The Effectiveness of Pulsed Electromagnetic Field Therapy on Muscle Strength and Function in Patients With End-stage of Knee Osteoarthritis Patients: a Randomized Controlled Trial

Knee osteoarthritis (OA) is one of the most common chronic degenerative joint conditions affecting our ageing population. It is widely stated that OA is the leading cause of disability in elders due to discordant symptoms, such as pain and stiffness. Radiographic evidence of OA increased with age, from 8% in subjects younger than age 50, to over 60% in subjects aged 60 or above. Typically, conservative therapies that target symptoms are recommended as first- and second-line treatments for knee OA to reduce pain, stiffness, and activity limitations. However, when conservative therapies fail, they would then require total knee replacement (TKR). In 2022 to 2023, there were over 34,000 patients on the Hospital Authority (HA) waiting list for TKR. With only 3389 TKRs being performed, the nominal waiting time for TKR was outrageously long, 122 months in Hong Kong, as compared to an average of 9 months in Canada. Despite the efforts from the government to establish more joint replacement centres, the number of patients suffering from end-stage OA knees and requiring surgery will increase significantly as the population ages. Toward those requiring TKR, the excruciating pain would further cause significant functional impairment and lower health-related quality of life, which could eventually affect post-surgery outcomes. Although TKR appears to be an effective treatment in most people with end-stage Knee OA, 20%-40% of individuals remain dissatisfied. This is due to reduced leg strength occurring years after surgery, impaired functional capacity like poorer walking performance, greater deficits in physically demanding tasks such as stair climbing and poor performance of domestic duties .

The role of knee-extensor strength in the end-stage of Knee OA Knee-extensor muscle weakness has been regarded as a risk factor for knee OA. As shown, end-stage knee OA patients awaiting TKR had 35% reduced knee-extensor strength compared to healthy, age-matched individuals. In addition, pre-operative knee-extensor strength has also been found to be a predictor of postoperative functional ability up to a year following surgery. On average, patients would lose an additional 80% of their pre-operative knee-extensor strength shortly after TKA. Collectively, these data highlight the importance of maintaining preoperative knee-extensor strength in the end-stage of knee OA awaiting TKR and suggest that the improvement of knee-extensor strength may postpone the need for surgery and increase the ability to perform functional activities after TKR at the same time.

The role and limitation of prehabilitation before TKR The concept of preparing the body for a stressful event, such as surgery, has been named "prehabilitation". Prehabilitation was reported to positively affect knee OA symptoms and support patients' self-management of their knee OA condition, potentially postponing the need for surgery. As supported by the latest systematic review, it is important to focus on knee extensor muscle strength when evaluating the effects of prehabilitation before surgery in patients eligible for TKR. The review found that prehabilitation exercise could help to moderately increase knee extensor muscle strength and physical function and reduce pain. Moreover, a 30-40% increase in knee-extensor strength has been suggested to improve knee pain and disability. In conclusion, current prehabilitation has limited effects on improving sufficient knee extensor muscle strength.

Potential role of PEMF PEMF treatment utilizes a pulsed electromagnetic field to stimulate mitochondrial activity in skeletal muscle. Our group (Prof. Alfredo Franco-Obregon) showed that brief 10-minute exposure of 1 mT amplitude of PEMF (Quantum Tx) on myoblast in vitro could activate myogenesis. This can lead to a boost in repair and muscle regeneration via the release of myokines. Additionally, it plays an important role in regulating the production and secretion of myokine. Therefore, it is hypothesized that PEMF exposure, on top of regular exercise training, may promote the secretion of myokine and in turn promote muscle regeneration. These findings laid grounds to implement PEMF treatment for end-stage knee OA patients to enhance muscle regeneration in periods where limited physical activity is occurred. Also, this may help to set up a treatment regime for the PEMF device to impose myogenic effects, including exposure time per session, the number of treatment sessions and the duration of treatment.

Aims