The role of pulsed electromagnetic therapy after knee arthroplasty

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Background

Successful joint replacement surgery depends on medical (implant type, design, and material; surgeon skills, rehabilitation program, etc.) and biological factors (inflammatory reaction, pain, tissue and bone swelling, and individual patient characteristics) [1–3]. Postoperative inflammatory reaction is the physiological basis of healing. However, if left unmanaged, it leads to irreversible fibrotic tissue injury, which is often associated with a pronounced local inflammatory reaction caused both by the underlying osteoarthritis and the surgical trauma, resulting in chronic pain, local swelling, and joint stiffness [4].

Despite the continuous improvement of biomaterials, surgical indications and methods, there is an alternative approach of stimulating the intrinsic bone regeneration using adjuvant therapy. It can accelerate and enhance bone ingrowth, reduce pain, and improve clinical outcomes. In this regard, approaches that increase the treatment efficacy by directly influencing bone growth and remodeling, such as pulsed electromagnetic fields (PEMF), are of interest.

In recent years, PEMF-based physiotherapy has gained popularity due to the study of cell membrane involvement in stimulating bone regeneration. Physical agents, through cell membrane components, trigger intracellular events that lead to a biological response. Preclinical studies have shown that PEMFs activate membrane receptors and transmembrane channels, which may stimulate bone cell function, bone mineralization, and bone repair and can reduce inflammation [5]. PEMF therapy has a pronounced anti-inflammatory effect on the entire joint. This effect inhibits catabolic activity and promotes the production of anabolic factors, thereby stimulating the cartilage matrix synthesis, exerting a chondroprotective and trophic effect on the subchondral bone, preventing sclerosis, and promoting the resorption of bone edema [6]. The production of catabolic and proinflammatory mediators, such as cytokines, nitric oxide, prostaglandin E2, and neuropeptides, in the inflamed synovium is directly associated with cartilage matrix degeneration and clinical symptoms. In particular, a significant inverse correlation was found between the intra-articular concentration of interleukin-6 (IL-6) as measured in the patient’s joint after total knee arthroplasty (TKA) and the patient’s postoperative functional recovery during the first month of observation [7]. For early postoperative functional recovery of the joint, the local inflammatory reaction is prognostically more important than systemic manifestations of inflammation. This is especially relevant in case of repeated surgeries (e.g. implant revisions) as inflammation management therapy (including physical therapy) is extremely important in preventing possible complications of total joint arthroplasty (implant instability, poor healing of bone defects, etc.). Therapeutic interventions with a specific synovial reaction after surgery may improve disease symptoms and prevent structural progression of joint osteoarthritis (OA) [6, 8]. The synovial membrane is a promising target for new strategies to prevent structural changes and manage clinical symptoms.

PEMFs modulate adenosine and are able to enhance the function of this endogenous agonist. In particular, PEMFs were shown to inhibit the release of PGE2, IL-6, and IL-8, while promoting the production of IL-10 in human synovial fibroblasts suffering from osteoarthritis. These effects are mediated by activation of adenosine receptors A2A and A3 [9]. PEMFs also reduce IL-1β level by enhancing proteoglycan synthesis and chondrocyte proliferation, especially in combination with insulin-like growth factor 1 (IGF-1), which plays a key role in the anabolic processes of joint metabolism [10].

Recent studies have shown that PEMFs promote osteogenesis in human mesenchymal stem cells (hMSCs) by increasing osteocalcin, alkaline phosphatase activity, and matrix mineralization [11]. It activates the Notch pathway, promoting interactions between PEMF and the osteogenic microenvironment. At the early stages of osteoblast differentiation, PEMFs regulate the expression of potential-dependent Ca2+ channels and the intracellular calcium. Experiments in vivo show that this leads to increased bone tissue formation [12].

Multiple recent clinical studies found that the use of PEMF after various joint surgeries (including chondral abrasion, perforation, autologous chondrocyte implantation, anterior cruciate ligament reconstruction, and total knee arthroplasty) contributed to a more rapid and significant postoperative pain reduction during the first month, according to the Visual Analog Scale (VAS) [13].

This prospective, randomized, placebo-controlled study aimed to evaluate the pain relief efficacy of PEMF in patients after medial unicompartmental knee arthroplasty (UKA) compared to sham PEMF. The secondary aim was to determine the changes in the knee joint function in 1, 2, 6, 12, and 36 months post-operative. It is assumed that the PEMF group will have significantly less pain than the control group throughout the observation period.

Materials and methods

Study design

Prospective, randomized, placebo-controlled clinical study.

Study setting

Knee arthroplasty (KA) was performed by surgeons specializing in knee arthroplasty at the Orthopedic Department of the State Budgetary Institution of the Ryazan Region Ryazan Regional Clinical Hospital and the Surgical Department of the State Budgetary Institution of the Ryazan Region Municipal Clinical Hospital of Emergency Medical Care (Ryazan).

A physiotherapist was responsible for outpatient postoperative management of patients at the Rehabilitation Department of the State Budgetary Institution Ryazan Regional Clinical Hospital and Elamed Medical Center (Ryazan) with the advisory assistance of the Federal State Budgetary Educational Institution of Higher Education Ryazan State Medical University of the Ministry of Health of Russia. Study duration: October 2018 to June 2024.

Eligibility criteria

Inclusion criteria:

• Men and women aged 60 to 85 years;
• Patients who had chronic and debilitating knee pain before surgery with pain syndrome assessed by VAS ≥ 7;
• Medial osteoarthritis with max stage 3 varus or valgus deformities;
• Knee joint range of motion greater than 100° with less than 10° flexion contracture;
• Integral anterior and posterior cruciate ligaments with a preserved lateral meniscus;
• Constant use of painkillers during the last year;
• High tolerance to pulsed magnetic fields.

Exclusion criteria:

• Patients with a history of knee joint infection;
• Patients with total hip arthroplasty;
• Patients with bone marrow edema of the medial knee joint;
• Rheumatoid arthritis, autoimmune and systemic diseases;
• Oncological diseases;
• Body mass index over 30 kg/m2;
• Revision surgeries and the history of surgeries on the affected knee (except arthroscopic meniscectomy);
• Patients with pacemakers;
• Patients with magnetic field intolerance;
• Patients who did not sign voluntary informed consent to participate in the study.

Withdrawal criteria:

• Patient refuses to participate during the clinical study;
• Complications and adverse reactions developed during the study;
• Patient’s death.

Intervention

The study cohort included 72 participants, including 29 males and 43 females aged 62 to 83 years (mean age 69.3 years), who were undergoing rehabilitation after knee arthroplasty at the Rehabilitation Department of the State Budgetary Institution Rostov Regional Clinical Hospital and Elamed Medical Center.

To obtain two groups without statistical differences at baseline, patients were randomized to the control group (sham PEMF) or the treatment group including PEMF therapy using a web-based computer program (www.randomization.com/), which was stratified by sex (female and male), age (50–75 years; 75–85 years), and smoking status (yes/no). All patients signed informed consent to participate in the study.

Patients were randomly divided into two groups. The first (treatment) group included 36 patients who underwent PEMF therapy and standard NSAID therapy; the second group (control group) included 36 patients who underwent sham PEMF therapy and standard NSAID therapy.

Pulsed Electromagnetic Therapy

Patients in the treatment group were instructed to use the PEMF generator (ALMAG+, Russia) for 20 minutes 4 times a day for 3 months [14]. Treatment began 3–7 days after surgery in the patient’s home setting. ALMAG+ is a serial device produced by the Elatomsky Instrument Plant JSC (registration certificate No. RZN 2017/6194 dated November 23, 2017). The device generated an alternating pulsed magnetic field with a pulse frequency of 6.25 Hz and a magnetic induction of 20 ± 6 mT. PEMF course using the ALMAG+ device lasted for three weeks, followed by a 1-day break. Basic mode No. 1 was used; the flexible inductor line of emitters was fixed around the operated knee joint with elastic bands and the N poles of the inductors in the line were positioned towards the patient’s body. Study participants were able to discontinue treatment in case of adverse events, such as skin irritation or a burning sensation.

Patients in the control group used a sham PEMF device. The fully equipped serial ALMAG+ device was used as a placebo. When the placebo device was turned on, it indicated the operating mode, but the magnetic field generation was turned off, allowing to simulate the operation of a real device.

Surgery and Rehabilitation

All surgeries were performed at the Orthopedic Department of the State Budgetary Institution of the Ryazan Region Ryazan Regional Clinical Hospital and the Surgical Department of the State Budgetary Institution of the Ryazan Region Municipal Clinical Hospital of Emergency Medical Care by experienced surgeons with experience in knee arthroplasty using minimally invasive surgical techniques in all patients. All patients underwent partial KA using the Zimmer Biomet implant (Germany) and minimally invasive surgical instruments (Oxford®, USA) [15]. This technique used a medial parapatellar approach without patellar dislocation. Both groups of patients followed the same rehabilitation protocol, including passive mobilization from day 1 after surgery and active progressive joint mobilization with assisted walking using two crutches from day 2. Each patient gradually increased the walking load, followed by isometric exercises to increase muscle tone until the walking aids were abandoned.

Outcomes registration

Clinical assessments

Clinical observation involved two rehabilitation therapists who were not engaged in the arthroplasty. The patients’ status was assessed before surgery and later at periods corresponding to 1, 2, 6, 12, and 36 months (± 5 days) after surgery. Clinical assessments included the Visual Analog Scale (VAS) for pain, the Oxford Knee Score (OKS), and the Short Form-36 (SF-36) health survey. Joint swelling was determined by measuring the knee circumference at the middle of the patella in the supine position using a regular tape measure. Joint swelling was assessed according to Soderberg et al. [19] using the following scores: 40, no difference in knee circumference; 30, < 0.5 cm; 20, 0.5 to 1 cm; 10, 1 to 1.5 cm; 0, if the difference in knee circumference > 1.5 cm. For subjective swelling assessment, we used questions from Section 2 (Joint Swelling) of the Cincinnati Knee Rating System; the score ranges from 0 (constant massive swelling with simple walking) to 10 (no swelling) in increments of 2 [20]. Nonsteroidal anti-inflammatory drug (NSAID) use prescribed by the physician after surgery was recorded at each follow-up visit. Finally, during the third follow-up year, surveys were conducted to examine each patient’s pain persistence, limitation of activities of daily living, and NSAID use; complications were recorded for each patient. All physicians responsible for assessing clinical outcomes were blinded to the patients’ treatment status.

Satisfaction Proportion

To assess whether the PEMF could increase the proportion of patients with the highest satisfaction score after KA, we examined the proportion of patients who had the predetermined score in each clinical assessment in the treatment and control groups at 6 and 12 months.

For objective knee circumference measurement, the highest outcome satisfaction was 40 cm; for subjective swelling assessment, the highest outcome satisfaction was 10; for Oxford Knee Score, the highest satisfaction score was 45; for VAS, the highest satisfaction score at 6 months was < 1 and < 0.5 at 12 months [21].

Ethics approval

In this study, all procedures involving patients were performed in accordance with the ethical standards of the Institutional Research Committee and the amended 1964 Helsinki Declaration or comparable ethical standards. The consent to the protocol and the clinical study program were approved by the local Ethics Committee of the Ryazan State Medical University (Minutes No. 11 dated October 5, 2018). All participants completed and signed informed consent to participate in the study.

Statistical analysis

A power analysis was performed by the primary pain assessment using VAS based on several studies of the effects of electromagnetic fields on pain in the literature. A two-tailed Fisher’s exact test was used as a test statistic. Test significance was taken at 0.05. Descriptive analysis of quantitative variables was performed by calculating the mean value and standard error in each group; categorical variables were presented as frequency and percentage. The normality of distribution of the two samples was tested using the Kolmogorov–Smirnov test and all quantitative variables had normal distribution. The two groups were compared at baseline and at all follow-up observations using a two-tailed Student’s t-test. Homogeneity of sample variance was assessed using the Levene’s test. Analysis of changes in quantitative variables in each group for an individual subject relative to baseline values was performed using a paired, two-tailed Student’s t-test with multiple correction by the Bonferroni test. Categorical variables of the groups were compared using contingency tables and the chi-square test. Statistical analysis was performed using SPSS v. 22 (USA).

Results

Samples size calculating

The group sample size of 36 participants in the treatment group and 36 participants in the control group had a power of 91%, allowing to detect a difference between group proportions of 40% when the percentage reduction in the treatment group (PEMF group) was assumed at 43% under the null hypothesis and 83% under the alternative hypothesis.

72 patients (36 in the PEMF group, 36 in the control group) with an indication for the knee arthroplasty (KA) were assessed by compliance criteria. Of the 36 patients included in the PEMF group, two patients have withdrawn from the study within a month of observation for personal reasons (refusal to continue the study). Of the 36 patients in the control group, two were excluded from the study within 36 months of observation; one patient died and the other underwent surgical revision of the implant due to a traumatic event. The flow chart of the study design is shown in Fig. 1.

 

Fig. 1. Flow chart of the study design (according to the recommendations of STrengthening the Reporting of OBservational studies in Epidemiology, STROBE). © Eco-Vector, 2025.

 

Clinical status of patients

At baseline, both groups were homogeneous by the following patient characteristics: age (p = 0.4578), sex (p = 0.48), weight (p = 0.4124), height (p = 0.4234), smoking status (p = 0.7578), VAS (p = 0.2532), objective knee circumference (p = 0.4786), subjective swelling assessment (p = 0.2462), and Oxford Knee Scale (p = 0.3425). The only statistical difference between the two groups was the SF-36 Global Health Survey score, which was higher in the PEMF group (p = 0.0231). Over the 3 months of the study, patients in the treatment group used the PEMF device an average of 126 times over 42 hours. Patients in the control group used the sham PEMF device an average of 128 times over 43 hours. Detailed results are shown in Table 1.

 

Table 1. Characteristics of the study cohort of patients

Patient characteristics	Control group	Treatment group	р
Patients included / excluded	36/2	36/2	―
Sex (male / female)	15М/21Ж	14М/22Ж	0.4800
Age, years	68±8	70±7	0.4578
Weight, kg	76±13	78±15	0.4124
Height, cm	167±6	168±7	0.4234
Smoking status (Y / N)	11/23	10/24	0.7578
VAS	7.7±1.6	7.3±1.7	0.2532
Knee circumference, cm	22.8±7.6	21.7±6.5	0.4786
Subjective knee swelling assessment, points	2.5±3.3	2.6±3.5	0.2462
Oxford Knee Score, points	20.2±5.8	21.2±6.4	0.3425
SF-36, points	48.2±10.5	54.8±12.2	0.0231

Note here and in Table 2: The values are presented as M±std. Statistically significant values (p <0.05) are shown in bold.

 

Visual Analog Scale

Preoperative pain was high in both groups (PEMF group: 7.3 ± 1.9; control group: 7.5 ± 1.7; p = 0.2172). Table 2 shows that the VAS score decreased during follow-up in both groups and significant differences between the groups were observed at 6 months (0.9 ± 0.3 vs. 0.5 ± 0.3; p = 0.0143), 12 months (0.6 ± 0.3 vs. 0.3 ± 0.2; p = 0.0004), and 36 months (0.6 ± 0.2 vs. 0.5 ± 0.2; p = 0.0213) follow-up with better outcomes in the PEMF group.

 

Table 2. Average VAS values, objective and subjective assessments of knee joint swelling at different time points

Time (months)	Control group	Treatment group	р
VAS
0	7.5±1.7	7.3±1.9	0.2172
1	3.8±1.9	3.2±1.5	0.1034
2	1.8±0.8	1.5±0.9	0.1345
6	0.9±0.3	0.5±0.3	0.0143
12	0.6±0.3	0.3±0.2	0.0004
36	0.6±0.2	0.5±0.2	0.0213
Knee circumference
0	21.9±8.6	22.6±7.3	0.4674
1	25.3±7.2	25.2±6.5	0.4843
2	30.1±8.2	29.4±5.8	0.3452
6	35.8±5.1	32.4±5.2	0.0232
12	37.8±4.8	34.6±4.7	0.0016
36	38.2±4.2	34.2±5.1	0.0004
Subjective joint swelling assessment
0	2.8±3.5	2.2±3.3	0.2342
1	2.1±3.1	1.4±2.2	0.0787
2	5.7±2.8	4.1±2.6	0.0064
6	8.5±1.4	7.0±1.8	0.0005
12	9.4±1.2	8.1±1.2	0.00022
36	9.3±0.8	8.6±1.3	0.00031

 

NSAIDs use

At 1 month post-KA, the percentage of patients taking NSAIDs in the PEMF and control groups was 73 and 91%, respectively (p < 0.05) (see Fig. 2). At 2 months of observation, a significant decrease in the need for medications was noted; NSAIDs were used by 14% of patients in the PEMF group compared to 38% in the control group (p < 0.05). At 6, 12, and 36 months, no patient in either group required NSAIDs.

 

Fig. 2. Percentage of NSAIDs used in the comparison and PEMF groups, demonstrating a statistically significant difference according to the chi-square criterion during the first and second postoperative months in favor of the PEMF group. *p <0.05. © Eco-Vector, 2025.

 

Joint swelling

Objective knee circumference measurement in accordance with Soderberg et al. [22] showed a significant difference in swelling in the PEMF group vs. the control group (p < 0.05) at 6 (32.4 ± 5.2 vs. 35.8 ± 5.1; p = 0.0232), 12 (34.6 ± 4.7 vs. 37.8 ± 4.8; p = 0.0016), and 36 (34.2 ± 5.1 vs. 38.2 ± 4.2; p = 0.0004) months.

Subjective knee circumference measurement showed a significant difference at 2 (4.1 ± 2.6 vs. 5.7 ± 2.8; р = 0.0064), 6 (7.0 ± 1,8 vs. 8.5 ± 1.4; р=0.0005), 12 (8.1 ± 1.2 vs. 9.4 ± 1.2; р = 0.0002), and 36 (8.6 ± 1.3 vs. 9.3 ± 0.8; p = 0.00031) months with higher values and, consequently, better outcomes the PEMF group (p < 0.05). Detailed results are shown in Table 2.

Oxford Knee Score

The Oxford Knee Score showed significantly higher results in the PEMF group throughout all observation periods compared to the control group, indicating a better condition of the knee joints in the first group (see Fig. 3). At 1 month postoperatively, the average Oxford knee score was 21.3 ± 4.2 in the PEMF group and 19.1 ± 3.9 in the control group (p = 0.0258); 34.7 ± 4.2 vs. 30.6 ± 4.6, respectively (p = 0.0014) at 2 months; 44.2 ± 2.8 vs. 40.7 ± 3.1, respectively (p = 0.0003) at 6 months; and at 12 months, OKS was 46.4 ± 2.2 in the PEMF group and 43.4 ± 2.7 in the control group (p = 0.0002). Finally, at 36 months, the mean OKS was 46.9 ± 1.7 in the PEMF group and 44.5 ± 2.7 in the control group; p = 0.0144.

 

Fig. 3. Oxford Knee Score during the study period, showing a higher clinical score during each follow-up in favor of the treatment group. *p <0.05. © Eco-Vector, 2025.

 

SF-36 Global Health Survey score, localization of pain in the body, and its physical intensity

Statistical differences between the two groups were recorded at baseline (p = 0.0121), resulting in a significantly higher score in the PEMF group in each observation period (p = 0.004). Hence, two specific items (bodily pain and role limitations) from the SF-36 survey were analyzed separately. Detailed results are shown in Table 3.

 

Table 3. Average indices of localization of pain in the body and physical intensity of pain according to the SF-36 scale at different points in time

Time (months)	Control group	Treatment group	р
Bodily pain localization (SF-36)
0	41±13	36±10	0.0572
1	49±11	43±11	0.0079
2	58±10	55±11	0.1335
6	77±11	72±10	0.0346
12	92±12	80±12	0.0009
36	86±11	77±12	0.0021
Physical pain intensity (SF-36)
0	24±32	16±28	0.1243
1	12±27	3±9	0.0347
2	32±37	17±22	0.0243
6	81±26	62±23	0.0013
12	93±12	75±24	0.0003
36	87±21	78±29	0.0483

 

The changes in body pain sensation showed more obvious results, revealing significant (p < 0.05) improvement in the PEMF group at each postoperative observation, which confirmed the VAS score, except for two months postoperatively (p = 0.1345). Physical functioning was statistically better in the PEMF group at each postoperative observation (p < 0.05).

Satisfaction percentage

Significant differences between the two groups were recorded between 6 and 36 months of observation with a higher satisfaction percentage observed in the PEMF group (p < 0.05). The analysis is shown in Table 4.

 

Table 4. Satisfaction percentage in two patient cohorts

Targets	Control group, %	Treatment group, %	р
Satisfaction percentage at 6 months
Joint swelling (score = 40)	32	58	0.0354
Subjective swelling assessment (score = 10)	5	31	0.0041
Oxford Knee Score (score = 45)	12	45	0.0029
VAS (score < 1.0)	46	75	0.0283
Satisfaction percentage at 36 months
Joint swelling (score = 40)	42	78	0.0018
Subjective swelling assessment (score = 10)	40	75	0.0036
Oxford Knee Score (score = 45)	62	89	0.0236
Satisfaction percentage at 12 months
VAS (score < 1.0)	32	88	<0.0012

 

Adverse events

No adverse events associated with PEMF therapy were reported during follow-up visits.

Discussion

The primary aim of the study was to evaluate pain relief in patients after knee arthroplasty (KA) with a mobile medial implant and subsequent PEMF stimulation compared to a placebo control group. During all observation periods, the PEMF group showed less pain, lower NSAID doses, and higher clinical status and satisfaction scores (objective and subjective swelling, SF-36, and knee score).

Our study showed that PEMF after KA could further improve outcomes after such surgeries. In fact, despite the advances of the last 10 years and the proven benefits of minimally invasive KA, surgeons have limited use of PEMF physiotherapy at the rehabilitation stages. This is likely due to concerns regarding survival, patient selection, ideal posture, and joint function [22]. Despite multiple causes for complaints post-KA, the decision to use PEMF therapy should be made early in rehabilitation, before the pain becomes chronic [23]. We believe that PEMF therapy may be an important adjunct to the postoperative period to avoid chronic pain by preventing the detrimental effects of KA-induced inflammation of joint tissues, resulting in short-term and long-term benefits for patients. According to Adravanti et al. [24], PEMF can be considered as part of surgical and postoperative treatment.

Analysis of various study reports on survival in more than 500 cases of medial KA showed that 10-year survival rates of 93–98% were reported with subjective assessments ranging from good to excellent [25]. However, these satisfactory results surpass the results of recent global and national registries, where the 10-year survival rate ranges from 81 to 88% [26].

Baker et al. [27] demonstrated that knee pain is a more common cause for revision after partial knee arthroplasty than after total knee arthroplasty, but the reasons for this finding are still unclear. As other causes of failure have similar levels in cohort and registry studies, a possible explanation is that some patients with unexplained pain have an (early) progression of osteoarthritis (OA). Park et al. [28] found that in several patients with unexplained pain, the progression of OA in other areas was not visible in X-ray images but was always visible with magnetic resonance imaging, including 82% of patients with even stage 3 and 4 OA. It suggested that in some cases, unexplained pain might be caused by the progression of OA.

Our study showed a significant reduction in VAS score after PEMF throughout the entire observation period, reducing the risk of failure due to pain and increasing the share of patients with the highest satisfaction score after a proven surgical treatment.

To the best of our knowledge, this is the first randomized placebo-controlled study that analyzes and reports PEMF outcomes after medial KA with a mobile implant, although several reports have already confirmed the efficacy of this treatment after orthopedic surgery [24, 29].

In particular, in 2014, Adravanti et al. [24] compared the clinical outcomes of 33 patients who underwent KA, randomized to a control group or a PEMF group. Postoperative PEMF therapy was performed for 4 hours daily, for 60 days. The patients’ status was evaluated before surgery and then during time intervals corresponding to 1, 2, and 6 months postoperatively using international scores [24]. At 1 month post-KA, VAS pain score and knee swelling were assessed by the differences between knee circumference according to Soderberg et al. [19] and knee function scores (Knee Society Score, KSS); the outcome was significantly better in the PEMF group compared to the control group.

Adravanti et al. [24] showed that at 1 month post-KA, the pain significantly reduced in both groups compared to the preoperative level, although it was more pronounced in the PEMF group (61%, p < 0.001, and 26%, p < 0.05, for the treatment and control groups, respectively). Indeed, at 1 month of observation, a significant difference was recorded between the groups in favor of the PEMF group (p < 0.05). Pain was significantly lower in the PEMF group at 6 months of observation (p < 0.05) with a 90% pain reduction compared to baseline in this group. Moreover, three years postoperatively, severe pain and intermittent walking limitations were reported in significantly fewer patients in the PEMF group compared to the control group [24].

Previously, Moretti et al. [30] aimed to determine whether PEMF therapy could be used to reduce pain and accelerate recovery of patients post-KA. Preoperatively, no differences were observed between groups by age, sex, weight, height, knee joint score, VAS, SF-36, and joint swelling, except for the functional score. In the PEMF group, the functional KSS score was significantly higher during the 12-month observation period compared to the control group at 2 months (66.0 ± 28.7 vs. 40.4 ± 17.5, p < 0.0001), 6 months (80.0 ± 19.4 vs. 51.0 ± 18.2, p < 0.0001), and 12 months (87.3 ± 16.8 vs. 55.0 ± 33.2; p < 0.005). Significant differences between the groups were also observed in the SF-36 health survey; higher values were noted in the PEMF group at 2 months (65.8 ± 15.2 vs. 32.5 ± 9.2, p < 0.0001), 6 months (75.1 ± 9.6 vs. 49.5 ± 17.2, p < 0.0001), and 12 months (76.3 ± 8.7 vs. 59.7 ± 19.6, p < 0.05). Moreover, VAS scores were significantly lower in the treatment group compared to the control group at all control visits at 1 month (2.4 ± 1.6 vs. 4.9 ± 1.8, p < 0.0001), 2 months (1.1 ± 1.0 vs. 4.6 ± 1.8, p < 0.0001), 6 months (1.5 ± 2.8 vs. 5.6 ± 2.9, p < 0.001), and 12 months (0.5 ± 1.3 vs. 3.6 ± 3.9, p < 0.05). In the PEMF group, the use of NSAIDs was lower and joint swelling resolved more quickly compared to the control group. The effect of PEMF therapy persisted after the device was discontinued [30].

Our study confirmed that PEMF therapy should be used for rehabilitation post-KA to reduce the surgery-induced inflammatory response to ensure pain relief and rapid functional recovery.

In 2019, La Verde et al. [31] conducted a randomized prospective controlled study of the effects of PEMF in reverse total shoulder arthroplasty, finding a better Constant Shoulder Score (CSS) and a lower VAS pain score at 1 month (CSS: 70 vs. 61, p < 0.05; VAS: 1.8 vs. 2.9, p < 0.05); 2 months (CSS: 76 vs. 63, p < 0.05; VAS: 1.6 vs. 2.6, p < 0.05), and 3 months (CSS: 78 vs. 67, p < 0.05; VAS: 1.5 vs. 2.2, p < 0.05) postoperatively in the group receiving PEMF therapy compared to the control group (p < 0.05). At 6 months of observation, no significant differences were found between the groups [31].

Given that one of the main reasons for the ineffective KA is the progression of OA in another joint, PEMF therapy post-KA is associated both with pain relief and the manifestation of contralateral OA degeneration due to inflammatory microenvironment in the joint. A recent systematic review of 15 studies by Yang et al. [32] shows results consistent with this study. This review proves that PEMF therapy has beneficial effects on pain, stiffness, and physical function in patients with OA compared to placebo. Similar results were confirmed by Vigano et al. [33]. Their analysis of 13 studies involving 914 unique patients assessed the effect of electromagnetic field treatment on knee OA symptoms using the Osteoarthritis Index, VAS and/or the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). After treatment, an overall reduction in pain scores was observed [33].

To better understand the clinical efficacy of PEMF after joint arthroplasty, it is important to analyze the function of electromagnetic fields in the joint microenvironment, especially in bone and cartilage. For cartilage, PEMF exposure enhances chondrogenic differentiation of mesenchymal stem cells (hMSCs) through direct activation of chondrogenic signaling pathways and an indirect paracrine mechanism mediated by the hMSC secretome. Thus, PEMF could be used as an adjuvant therapy to increase cartilage-specific gene expression and chondrogenic differentiation of hMSCs to overcome the obstacles associated with the use of growth factors in vivo [9]. Second, PEMF stimulation may also act as a chemotactic signal for hMSCs and chondrocytes, promoting cell migration to the injury site and tissue repair. Third, PEMFs have a strong anti-inflammatory and chondroprotective effect on cartilage tissue degenerated by the catabolic activity of proinflammatory cytokines [9].

Both the primary effects of PEMF on bone and enhanced vascular growth induced secondary to the release of angiogenetic factors such as IL-8, basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), and nitric oxide synthase. Moreover, PEMFs effectively increased the amount of new bone around porous hydroxyapatite implants in the proximal tibia of rabbits, although relatively minor effects were found in tricalcium phosphate implants, which was likely due to different pore sizes (the larger the diameter, the higher the stimulation efficacy) [9, 34, 35].

Finally, our study shows a significant reduction in drug consumption during PEMF therapy, especially NSAIDs. Analysis of these data is required to assess the socio-economic consequences associated with lower consumption of narcotic analgesic medications. In fact, the prevalence of chronic postoperative pain after knee arthroplasty varies across studies and affects approximately 15–20% of patients within 1–7 years postoperatively [35–37]. Based on qualitative structured interviews, Woolhead et al. reported that the majority of patients complained of postoperative pain, although 90% were satisfied with the surgery outcome [38]. The presented data indicate the importance of PEMF in the rehabilitation of destructive joint diseases [39].

Study limitations

Future studies should analyze whether PEMF can be a solution to reduce and improve pain, reduce medication consumption, promote rapid recovery, and most importantly, eliminate the side effects of NSAIDs with long-term use. Furthermore, the limited number of patients may explain the difference in SF-36 health survey scores observed at baseline between the two groups.

Conclusion

This study of PEMF therapy after medial KA showed that PEMF treatment was well tolerated and had no negative side effects. In addition, PEMF therapy contributes to significant clinical improvements, such as less pain, lower NSAID consumption rate, less swelling, and a higher percentage of patients reporting the highest satisfaction score after PEMF. Thus, pulsed electromagnetic fields result in significant pain relief after medial KA compared to the standard protocol. PEMF therapy provides a higher percentage of patients with the highest satisfaction score after medial KA compared to the standard protocol. Pulsed electromagnetic fields should be considered as a necessary element of the postoperative rehabilitation program.

Additional information

Funding source. This work was not supported by any external sources of funding.

Competing interests. The authors declare that they have no competing interests.

Authors’ contribution. Yu.Yu. Byalovsky ― development of the concept and design of the study, data collection, analysis and interpretation of results, critical revision of the draft manuscript with comments of intellectual content; S.I. Glotov ― development of the concept and design of the study, data collection, drafting the manuscript and creating its final version; I.S. Rakitina ― data collection, analysis and interpretation of results, drafting the manuscript and creating its final version; M.Yu. Mareeva ― literature review, statistical analysis. Thereby, all authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work.

Patients’ consent. Written consent obtained from all the study participants before the study screening in according to the study protocol approved by the local ethic committee.

About the authors

Yury Yu. Byalovsky

Ryazan State Medical University

Author for correspondence.
Email: b_uu@mail.ru
ORCID iD: 0000-0002-6769-8277
SPIN-code: 6389-6643

MD, Dr. Sci. (Med.), Professor

Russian Federation, Ryazan

Sergey Iv. Glotov

Ryazan State Medical University

Email: sergeyglot@mail.ru
ORCID iD: 0000-0002-4445-4480
SPIN-code: 7524-9816

MD, Cand. Sci. (Med.), Associate Professor

Russian Federation, Ryazan

Irina S. Rakitina

Ryazan State Medical University

Email: rakitina62@gmail.com
ORCID iD: 0000-0002-9406-1765
SPIN-code: 8427-9471

MD, Cand. Sci. (Med.), Associate Professor

Russian Federation, Ryazan

Marina Yu. Mareeva

Moscow Regional Scientific Research Institute of Obstetrics and Gynecology

Email: аkmoniiag@mail.ru
Russian Federation, Moscow

References

Supplementary files