## 2 Materials and Methods  
This single-site, open-label, prospective trial included 37 individuals, selected between December 2020 and June 2021 among patients treated for symptomatic knee OA at the outpatient rehabilitation clinic of the Paolo Giaccone University Polyclinic in Palermo. Inclusion criteria were as follows: age > 45 years; BMI > 25 kg/m\({}^{2}\); radiographic evidence of grade I and II knee OA according to the Kellgren-Lawrence classification; no infiltrative treatment in the previous 6 months; written consent for participation in the study. The exclusion criteria were as follows: concomitant use of anticoagulant and corticosteroid therapy, rheumatological diseases, major hip dysplasia, neurological or vascular diseases, and altered state of consciousness. We also chose to exclude patients with grade III and IV knee osteoarthritis according to the Kellgren-Lawrence classification, as several studies have shown that viscosupplementation performed in the early stages shows a better chondrocytes effect [23,24]. The study was conducted according to the ethical guidelines of the Helsinki declaration; information and data were handled in accordance with the Good Clinical Practice (GCP) guidelines. All participants signed an informed consent form at the time of the enrollment in order to collect clinical data. Patients were assessed at two timepoints: at baseline (T0) and 3 months after ultrasound-guided intra-articular injection of hybrid HA complexes (T1). As part of the initial assessment (T0), demographic information and clinical data regarding disease state were collected. With regard to clinical data, pain was assessed using the Visual Analog Scale (VAS), quality of life was self-reported via the 12-Item Short-Form Survey (SF-12), and disease severity was evaluated via the Western Ontario and McMaster Universities Arthritis Index (WOMAC) [25]. WOMAC is a 24-item self-administered questionnaire developed for hip and knee OA, assessing the three sub-fields of pain, stiffness, and physical function related to activities of daily living. Patients were furthermore asked to report analgesic intake, expressed as the number of days per week analgesics were required to achieve pain control. Lastly, patients' cardiocirculatory capacity was assessed via a 6 min walk test (6 MWT) in terms of distance traveled, and bioelectrical impedance analysis was performed to measure body fat and muscle mass percentages. Following initial assessment, patients underwent ultrasound (US)-guided intra-articular injection of hybrid HA complexes (Sinovial(r) H-L) in the knee joint every 15 days. The patient was positioned supine, with the knee slightly flexed or fully extended. With a sterile linear probe and using a transverse approach, the joint was scanned with the US. After lateral subluxation of the patella, a 21 G needle was introduced using a lateral approach, 1-2 cm below the superior lateral margin of the patella. Positioning was verified by aspiration, and then 2 mL of hybrid HA complexes (Sinovial(r) H-L) were injected into the knee joint, verifying intra-articular positioning in real time via US (direct visualization of viscous fluid or air bubbles). Having removed the needle, knee mobilization in flexion-extension was performed. Patients were subsequently reassessed after 3 months (T1), and clinical data on disease state post treatment were collected. To evaluate the effect of HA viscosupplementation in overweight knee OA patients, we assessed the following primary variables for statistically significant differences pre and post treatment:  
* pain severity, as assessed by VAS scale;
* disease severity, as assessed by the WOMAC Index;
* cardiovascular capacity, as assessed by distance walked in a 6 MWT. Three secondary variables were furthermore considered:
* quality of life, as assessed by SF-12;
* the percentage of fat and muscle mass, measured by bioelectrical impedance analysis;
* analgesic intake (days per week). Statistical analyses were performed using R software (R Core Team, 2013).