In orthopedic surgical practice, there is an increasing incidence of degenerative joint diseases, due to the rising average age of the population, as well as ligament injuries resulting from the growing participation in sports activities. The knee joint, in particular, is the most affected by these conditions, which, given their heterogeneous nature, impact patients across a wide age range.

Knee pathologies, often interconnected (with a higher incidence of degenerative diseases following ligamentous and/or meniscal injuries), are particularly debilitating for patients and entail high costs for the national healthcare system, which are expected to increase over time.

Scientific efforts in the field of knee surgery are therefore focused on achieving an increasingly detailed understanding of pathological conditions, as well as on the development of innovative technologies to support surgical and clinical practice.

Carrying out such analyses and developing new technologies inevitably involves experimental laboratory studies of joint tissues. The study of waste material obtained from surgical procedures represents a fundamental resource in this context and has always been used safely, with no additional invasiveness for the patient. A vast amount of information derived from laboratory analyses of discarded tissue has contributed to improving clinical practice and has led to the development of solutions that are now part of routine surgical use.

Recent technologies allow increasingly accurate evaluation of both the structure and mechanical properties of discarded tissue explanted during surgery. For example, structural assessment using micro-CT enables visualization and analysis of the interface between bone tissue, ligamentous structures, and surgical implants with micrometric precision. This makes it possible to determine tissue density, orientation, and material quality, distinguishing between different boundary conditions and physiopathological states of the tissues. Such analyses can also be performed under conditions close to those characterizing the joint in vivo, both in terms of tissue immersed in fluid and with respect to mechanical loads applied to deform the tissue. Furthermore, it is possible to reconstruct the structural interaction between human tissue and external materials used in surgery, such as screws, plates, anchoring devices, etc.

These instruments therefore make it possible to surpass the level of detail achievable with conventional diagnostic and research equipment used over the years, and to investigate with increasing accuracy the onset and progression of a pathology, the condition of the involved tissues, and to predict functional recovery of the treated site following the application of anchoring devices in the operating room. These new analyses also enable the study of innovative solutions for tissue repair and reconstruction, such as patient-specific customized devices and/or new materials produced using 3D printing technology, without posing any risk to the patient during surgery.

Inclusion Criteria:

• Total knee arthroplasty
• Kellgren-Lawrence grade II, III, or IV osteoarthritis;
• age < 85 years;
• BMI < 35

Exclusion Criteria:

• History/evidence of previous partial (unicompartmental) knee arthroplasty;
• positivity for viral infections such as HIV, HBV, or HCV;
• inability to provide informed consent.

Waste materials obtained from primary total knee arthroplasty procedures will be used. The collected material will mainly consist of osteochondral tissue from the patient's tibial plateau. This portion of tissue is routinely removed during the resection of the proximal (tibia) and distal (femur) bone components, which is necessary for the implantation of the prosthetic components. The resection and subsequent removal of the tibial plateau constitute a standard procedure and a mandatory step in primary total knee arthroplasty. This procedure will be performed intraoperatively by the medical staff of the coordinating investigator (Orthopaedic and Traumatology Clinic II). The waste material will be placed in a dedicated single-use container and transferred to the Research Center laboratories for analysis, in accordance with the above-mentioned internal procedure.