## 2 Methods of Diagnosing Cartilage Lesions
MRI uses specialised scales for assessing joints, in particular their damage, cartilage regeneration, and other intra-articular structures. The first of these is the whole-organ magnetic resonance imaging score (WORMS), which allows for the assessment of all joint structures, including, among others, joint cartilage, subchondral bone, menisci, ligaments, loose bodies in joints, and synovial fluid, and the presence of synovial fluid. Each of the elements is assessed on a scale from 0 to 4 where 0 means no changes and 4 means advanced changes. The particular importance of the WORMS scale is noticeable in the assessment of OA [47]. Another scale is the magnetic resonance observation of cartilage repair tissue (MOCART), which is used after cartilage surgery to assess the quality and effectiveness of its repair. The following elements are assessed: the thickness of the cartilage repair layer, structure of the repaired cartilage, surface of the cartilage repair, integration with adjacent cartilage, changes at the interface of the repaired cartilage with the subchondral bone, and the presence of cysts or fibrosis. The maximum score on the MOCART scale is 100, which indicates ideal cartilage repair [48]. MRI has its limitations, which include the high cost of the examination, availability, its time-consuming nature, and qualified personnel. Another important aspect worth mentioning in the context of MRI is gadolinium, which is used as a component of contrast administered intravenously to patients during the examination. The purpose of using gadolinium is to improve the quality of MRI images, which is particularly important during the assessment of pathological changes, such as inflammation and infections, tumours, and the diagnosis of vascular changes. However, the use of gadolinium can also generate side effects, which include allergic reactions, gadolinium retention in the body after repeated administration to the patient, and the occurrence of a rare disease nephrogenic systemic fibrosis (NSF) [49; 50; 51]. Table 1 presents a summary of the methods of diagnosing osteoarthritis. \begin{table}
\begin{tabular}{c c c c} \hline
**Diagnostic Method** & **Advantages** & **Disadvantages** & **Sources** \\ \hline \multirow{4}{*}{Radiography} & Noninvasive & Exposure to ionising radiation, & \\  & Inexpensive & Shows developed changes in the knee & \\  & High availability & joint, unable to diagnose small & \\  & Time & cartilage lesions in early stages & \\ \hline \end{tabular}
\end{table} 
Table 1: Comparison of diagnostic methods for knee osteoarthritis (OA). In 1987, [PERSON] et al. [66] proposed 'vibration arthrography' (VAG) as a noninvasive, sensitive, and inexpensive method for the early diagnosis of OA, which is based on the detection and recording of knee vibration emissions. During movements of the knee joint, elements moving relative to each other emit oscillations and vibrations caused by friction processes [30]. The knee joint during movements such as extension and flexion emits a signal that is called the VAG signal [30; 67]. The vibroacoustic signal during knee joint movement is influenced by changes in the mechanical properties, especially nodules, cracks, and cartilage defects, in subsequent stages of degenerative changes [30; 68]. Mechanical vibrations arise as a result of a change in the distribution of forces in the contact zones caused by cyclically changing loads on the joint elements. VAG enables early detection of cartilage micro-damage before it becomes visible on MRI. This noninvasive and cost-effective method can be used repeatedly, making it ideal for monitoring disease progression, such as osteoarthritis (OA), or assessing therapy effectiveness. The analysis of vibratory signals can also reveal biomechanical issues that may cause pain, even when no changes are visible on MRI or CT. Due to its affordability, noninvasive nature, and lack of radiation exposure, VAG is suitable for screening, helping to reduce the need for redundant and costly imaging studies.