## 2 Application Fields
### Joint Preservation  
The use of PEMFs also has a role in preserving the joint compartment. In fact, in vitro studies have obtained promising results on the possibility of cartilage repair through using electromagnetic fields [40; 41; 42; 43]. A meta-analysis regarding the application of low- and high-frequency electromagnetic fields in the presence of inflammatory degenerative joint diseases was recently conductedby [PERSON] et al. [17]. This review states that there is evidence for low-frequency PEMFs for these pathologies at the knee and hand level, obtaining an improvement in clinical symptoms and range of motion. The positive results for the improvement of joint inflammation and ligament lesion are also reported in the study conducted by [PERSON] et al. [44] in patients undergoing arthroscopic knee surgery for ACL reconstruction. In total, 60 patients were identified, divided into 31 treated with biophysical stimulation and 29 in the placebo group. All patients underwent ACL reconstruction with the use of a quadruple hamstrings semitendinosus and gracilis technique. At baseline, there were no differences in the International Knee Documentation Committee (IKDC) scores between the two groups. Based on interesting pre-clinical efficacy studies, a treatment protocol was developed which involved the use of the stimulator for 4 h a day, not necessarily consecutively, for 60 days. Treatment started within 7 days from the surgery. The authors observed a lower consumption of painkillers and an improvement in the SF-36 Health Survey score at 2 and 6 months. However, it is more complex to analyze the results of the IKDC score where, as reported by the authors, there are some confounding factors. The conclusion of the work is expressed favorably regarding the reduction of the inflammatory process and the improvement of the joint catabolic processes, with benefits to both the articular cartilage and the subchondral bone. For this reason, a rationale for their use after arthroscopic surgery is suggested, particularly in those subjects who need a rapid return to physical activity. In accordance with what has been stated, we also report the review conducted by [PERSON] et al. [45] considering works on athletes with high functional demands treated with PEMFs and extracorporeal shock wave therapy (ESWT). Even in this situation, biophysical stimulation reduced the inflammatory process, improving adherence to the physiotherapy program and the return to sporting activity in non-advanced forms of osteoarthritis (OA). The authors conclude that, although there are extremely interesting findings, it is essential to develop high-quality studies of athletes to draw stronger conclusions. However, [PERSON] et al. conducted a randomized prospective and double-blind study in patients with osteochondral degeneration and knee pain symptoms treated with microfractures in combination with PEMF. Patients with Grade I to IV cartilage lesions according to the Outerbridge classification were included in the study. Patients performed PEMFs for 6 h a day for 90 days. In the first month after surgery, the percentage of patients using nonsteroidal anti-inflammatory drugs (NSAIDs) was 26% in the active group and 75% in the control group (_p_ = 0.015). The KOOS (Knee Osteoarthritis Outcome Score) clinical evaluation showed higher values (better joint function) in the active group at both 45 days (73.6 \(\pm\) 10.3 vs. 70.3 \(\pm\) 14.9, ns) and 90 days (83.6 \(\pm\) 7.3 vs. 74.7 \(\pm\) 13.6, \(p\) < 0.05) from surgery. At 45 days, patients in the active group already showed a level of functional recovery that patients in the placebo group would show at 90 days, demonstrating a halving of the recovery time. At 3 years of follow-up, the number of patients showing functional limitations of the knee joint was significantly higher in the control group compared to the active group (87.5% vs. 37.5%) [36]. In 2016, [PERSON]. et al.