## 2 Methods of Diagnosing Cartilage Lesions  
To understand the need for research on the use of vibroarthrography in the diagnosis of knee osteoarthritis, it is necessary to analyse the diagnostic methods currently used for this purpose. These methods include physical examination, computed tomography (CT), radiography (X-ray), magnetic resonance imaging (MRI), and ultrasonic testing (UT) [30; 31; 32]. However, their reliability and accuracy in the assessment of cartilage damage is questionable. In addition, each of them has its own limitations, such as the high cost of the equipment. Radiography is the basis for the diagnosis of degenerative changes according to the Kellgren-Lawrence scale [33]. Factors that indirectly assess the quality of articular cartilage are assessed: the presence of osteophytes, as well as joint space narrowing, deformations of the joint surface, and subchondral bone hypertrophy [34]. The biggest disadvantage of this imaging modality is that it does not show cartilage, and only the bony changes that form after cartilage lesions occur can be appreciated. Moreover, no information about surrounding soft tissues can be acquired from conventional radiography [11; 35; 36; 35]. However, the advantages include low cost, high availability, and low patient exposure to ionising radiation. A more effective method is computed tomography (CT), which provides a more detailed image of the knee joint [37; 38]. This allows for a more precise assessment of the joint structure and degenerative changes. Unfortunately, as in the case of radiography, this method does not provide the best results in diagnosing the early stages of OA because it is not possible to obtain a direct image of the cartilage; it only allows for estimating signs of its damage based on bone changes. Additionally, the cost of computed tomography is much higher than radiography, and the patient is exposed to a dose of ionising radiation that is several to a dozen times higher than in radiography [39; 40]. In order to improve the visibility of the imaged elements, contrast-enhanced tomography of the knee joint is used. However, this requires prior preparation of the patient for the medical examination. The use of contrast during the examination also has an impact on the increased cost compared to regular computed tomography. It is also possible for the patient to experience a dangerous allergic reaction. Another method used in the early diagnosis of OA is ultrasound [41; 42; 43]. Its advantages are low cost, high availability, lack of radiation, and ability to perform a dynamic examination [39; 44]. Comprehensive assessment systems, i.e., standardised classification systems used in ultrasound, have been developed and validated to systematically describe and evaluate different organs and pathologies with an emphasis on the patient's inflammatory state. The use of ultrasound makes it possible to visualise the structure of the knee joint and detect cartilage and articular changes by obtaining an image in real time. Ultrasonography uses the Doppler imaging technique to assess blood flow in vessels. Power Doppler (PD), in particular, allows for the assessment of hyperaemia and inflammation occurring in the examined patient, which is a significant advantage of ultrasonography over other diagnostic methods. However, the use of ultrasound does not provide a high-quality image of the articular cartilage and soft tissues surrounding the knee joint, and the examination itself depends on the experience of the person performing it. The diagnostic method that is currently the most advanced and most effective in cases of articular cartilage damage is magnetic resonance imaging (MRI) [34; 42; 45; 46]. Using the MRI method, a very detailed image of the structure of the knee joint is obtained, which allows for the detection of damage in its initial phase of development. The obtained three-dimensional image of the knee joint allows doctors to more thoroughly assess the advancement of the disease.