Analysis of the Pathophysiological and Functional State of the Knee Joint

MRI images will be acquired for each subject using a high-field scanner (3T, Discovery MR750w3, GE Healthcare, UK) with sequences that will allow i) the analysis of the pathophysiological state of the knee cartilage, and ii) the identification and segmentation of the various leg muscles.

Regarding the investigation of joint tissues, quantitative sequences (e.g., T2 mapping) will be acquired using a specific coil, according to standard practice. MRI images related to the muscular aspects of the entire lower limb will be added to the previous ones-which will instead be focused on the region bounded by the femoral and tibial diaphyses-in order to obtain complete information in a single acquisition session with additional timing on the order of minutes. MRI images at the 12-month follow-up are specific to the study.

As per clinical practice, before gait analysis, muscle strength (generalized, not specific to the knee flexor and extensor muscles) will be measured through the execution of a hand grip test with a manual hydraulic dynamometer (Jamar, Sammons Preston Rolyan, USA). The measurement will be repeated three times, allowing a 1-minute rest between repetitions.

Patients will be asked to undergo a bioimpedance measurement (BIA BIVA 101 PRO, Akern, ITA) to estimate the muscle mass (residual) and fat mass for both lower limbs.

Gait analysis with electromyographic signal acquisition will be performed. Anthropometric measurements will be taken, and retroreflective markers will be placed on anatomical landmarks. Bipolar electrodes will be positioned on key lower limb muscles according to SENIAM guidelines. The test includes static calibration, walking, sit-to-stand-to-sit, and step-over tasks. Electromyographic signals will be monitored and analyzed for muscle activation and co-activation. The session will last 40-60 minutes and is study-specific.

Knee function and pain will be assessed using the WOMAC (Western Ontario and McMaster Universities Arthritis Index) and KOOS (Knee Injury and Osteoarthritis Outcome Score) scales. WOMAC is a self-assessment questionnaire with 24 questions divided into three subgroups evaluating knee pain, joint stiffness, and functionality during daily activities. KOOS evaluates symptoms, pain, daily activities, sports activities, and quality of life.

A dedicated data collection form will be used to gather all clinical information and study results. For each patient, a paper Case Report Form (CRF) will be completed. Additionally, all collected experimental data will be saved in a specially created folder on the Institute's secure server.