Knee osteoarthritis (gonarthrosis) is an extremely debilitating condition for affected patients, who experience progressive functional limitations with consequent impairment of daily activities and quality of life. Additionally, this condition represents a significant burden on the national healthcare system due to the severe functional limitations of affected patients and the high costs of interventions and devices used for prosthetic replacement. Knee replacement surgery is the gold standard treatment for gonarthrosis; however, this procedure carries a doubled risk of failure in patients under 60 years of age. Therefore, considering the high number of patients affected by early or intermediate-stage osteoarthritis at an age characterized by high functional demands, it becomes essential to identify treatment alternatives aimed primarily at resolving symptoms but also at slowing down the degenerative joint process, with the goal of delaying the need for prosthetic treatment as much as possible.

While various surgical solutions, including joint preservation procedures, have been proposed, clear evidence is still lacking regarding the effectiveness of conservative treatments in protecting and possibly regenerating the pathological articular cartilage that characterizes patients with gonarthrosis. In this scenario, quantifying the therapeutic potential of non-surgical treatment devices for patients with gonarthrosis is of considerable importance in the development of degenerative joint disease treatment. From this need arises the desire to verify the regenerative potential of available strategies for the treatment of joint pathologies.

Biophysical stimulation with variable intensity magnetic fields over time represents a therapeutic option supported by a solid body of scientific literature for the treatment of conditions associated with joint osteoarthritis such as bone edema and soft tissue distress. The medical device BB-02 (IGEA SpA, Carpi, Italy) is a certified medical device according to Regulation (EU) 2017/745 (MDR) for the treatment of inflammatory and degenerative tissue diseases. BB-02 is used for inflammation control and chondroprotection: chondroprotection refers to the set of pharmacological, physical, surgical, alone or combined treatments, aimed at preserving cartilage integrity or limiting damage due to degenerative, pathological, and traumatic processes, as well as inflammatory reactions. BB-02 therapy limits the degenerative effects of inflammation present in the joint environment after trauma or surgery. The medical device BB-02 extinguishes joint inflammation through an adenosine agonist action on the A2A receptor and exerts a strong chondroprotective effect. Extensive translational research has shown that biophysical stimulation with BB-02 therapy is capable of modulating cartilage metabolism (Massari L 2007).

In vitro, BB-02 therapy induces a significant increase in both chondrocyte proliferation in the presence of growth factors, such as IGF-1, and proteoglycan synthesis, even in the presence of inflammatory phenomena, such as IL-1β (De Mattei M 2003, 2004, 2009; Ongaro A 2011, Veronesi 2015). In vitro studies on neutrophils, synoviocytes, and chondrocytes have shown that BB-02 therapy increases the availability of adenosine A2A receptors and, acting as chondroprotective agents, reduces tissue damage due to the inflammatory response (Varani K, 2002, 2008, 2017). Stimulation with BB-02 therapy, by reducing the release of inflammation mediators involved in cartilage degeneration, such as inflammatory cytokines (IL-6 and IL-8) and lipid mediators of inflammation (prostaglandin E2), enhances the anti-inflammatory effect of individual adenosinic agonists A2A and A3 by increasing the release of anti-inflammatory cytokines such as IL-10 (Ongaro A 2012, Vincenzi F 2013). Synovial stem cells have shown a high chondrogenic potential; in culture, with appropriate chondroinductive supplements supplemented with TGF-β3, they are capable of differentiating in a chondrogenic direction. In a study conducted on these types of cells, chondrogenic differentiation was analyzed in the presence of inflammatory conditions, obtained by adding the culture medium with IL-1β (Ongaro A 2015), and BB-02 therapy. Stimulation is able to inhibit the inflammatory phenomenon and preserve the chondrocyte phenotype. These and other results have been confirmed in animal models of osteoarthritis where stimulation with BB-02 therapy has led to a reduction in the progression of osteoarthritic lesions in the knee (Fini M 2005, 2008, Veronesi F 2014). In sheep undergoing osteochondral transplantation, BB-02 therapy was able to promote the formation of new subchondral bone tissue, reducing areas of bone resorption, avoiding complete implant resorption (Benazzo F 2008). Evidence of an anabolic and trophic effect has been observed with high synthesis of anabolic factors, such as TGF-β, and inhibition of the synthesis of pro-inflammatory cytokines, such as TNF-α and IL-1β. In rabbits with osteochondral lesions, BB-02 therapy has been shown to be effective in significantly improving the quality of regenerated tissue, both bone and cartilage, in osteochondral defects in the presence of collagen scaffolds and bone marrow concentrate (BMC) (Veronesi F BMC Musculoskelet Disord. 2015). The anti-inflammatory activity of BB-02 therapy effectively counteracts the degenerative effect of IL-1β, significantly improving cartilage regeneration compared to non-stimulated lesions. Recently, the Columbia University group has demonstrated how BB-02 therapy is able to maximize the survival and functionality of osteochondral implants in tissue engineering methods (Stefani RM 2020). In clinical practice, in the conservative treatment of joint pathologies such as Bone Marrow Edema (Martinelli N 2015, Perugia D 2015), spontaneous osteonecrosis of the knee (Marcheggiani Muccioli G 2012), early-stage knee osteoarthritis (Gobbi A 2013), and patellofemoral pathology (Immarrone CS 2016), BB-02 therapy has been shown to be effective in resolving the area of bone marrow edema and improving joint functional recovery. Imaging diagnostics in the study of cartilage pathology can non-invasively confirm the presence of cartilage pathology, establish the degree of alterations, enable proper therapy planning (conservative or surgical), and verify its effectiveness over time. Conventional radiography (X-ray) is the most basic and cost-effective imaging technique and is used as a first-level investigation in the diagnosis of degenerative joint pathology, but it is of limited use in evaluating early stages and initial alterations of articular cartilage. The advent of magnetic resonance imaging (MRI), with its superior soft tissue contrast and multiplanar imaging capabilities, has solved many problems in imaging articular cartilage, providing non-invasive, both morphological and biochemical, information on the cartilage state. Morphological information provided by MRI includes both focal and diffuse cartilage lesions. MRI provides information such as thickness, volume, and three-dimensional morphology of the cartilage; biochemical information is represented by the ability to determine the content of water, proteoglycans, and collagen. Knowledge of this additional information is of great utility in understanding cartilage pathology and therefore in choosing therapeutic treatment.

In this study, we aim to evaluate the efficacy of two different therapeutic regimens with BB-02 therapy in patients still active in sports with initial cartilage damage. The present study aims to observe the effect of BB-02 therapy on cartilage through high-field MRI (3 Tesla, 3T) investigation capable of providing both morphological and biochemical information on joint structures. With 3T MRI, we will evaluate the knee articular cartilage before and after treatment, focusing on initial superficial lesions present before treatment, and at the end of therapy, assessing whether and to what extent they are repaired.

Two different therapeutic regimens of BB-02 therapy will be applied in the study: 4 hours a day for 30 days and 1 hour a day for 90 days.