## 1 Introduction
Arthroscopy is a surgical procedure that allows visual assessment of joint structure, including articular cartilage, using a camera that transmits images to a monitor. In the case of AC damage, arthroscopy can provide more precise information. During this procedure, the surgeon is able to see and evaluate the thickness, smoothness of the surface, the presence of cracks, defects or degenerative changes in the articular cartilage. In addition, it allows AC samples to be taken for histopathological analysis, which aids in the diagnosis of certain diseases of the knee joint. Arthroscopy serves mainly as a therapeutic tool; as a surgical procedure, it can involve the risk of complications, such as infection, bleeding, infection of the joint, or damage to nerves or blood vessels. Due to the limitations of the above-mentioned methods, there is growing interest in so-called alternative diagnostic methods to assess the mechanical and biochemical properties of AC. Magnetic resonance elastography (MRE) is a method that illustrates the distribution of tissue stiffness based on shear wave propagation [30]. On the other hand, advanced MRI techniques in the form of T1\(\rho\)- or T2-mapping or dGEMRIC (delayed gadolinium-enhanced MRI of cartilage) make it possible to detect changes in the collagen, proteoglycan and water content, parameters that are associated with early degradative changes in AC [31; 32]. Real-time assessment of AC mechanical susceptibility and monitoring of OA progression is possible using ultrasound elastography [33]. A significant method to provide information regarding changes in the mechanical properties of the joint surface is vibroarthrography (VAG), which involves recording the vibrations emitted by the joint during movement [34]. The use of VAG is particularly useful in the evaluation of early changes in OA. Optical techniques can also be used, such as optical coherence tomography (OCT), which involves imaging with a resolution comparable to in vivo histology of the AC microstructure [35]. On the other hand, the use of Raman spectroscopy makes it possible to obtain information on the molecular composition of AC, such as the distribution of proteoglycans and collagen, which can be used as a biomarker of degeneration [36]. Another continuously developed approach is modal analysis, which makes it possible to assess the dynamic mechanical properties of AC, which in turn may be altered by tissue degeneration [37]. Although alternative methods of AC diagnosis are in the experimental research phase, they nevertheless show potential for the detection of early degenerative changes. The aim of this paper is to analyse the mechanical parameters of AC and to assess their changes during degradation processes such as osteoarthritis. The suitability of classical as well as alternative diagnostic methods to detect and monitor changes in the structure, biomechanical and biochemical properties of AC is presented. The aim of the study is also to indicate possible directions for the development of diagnostics based on mechanical parameters and their correlation with the patient's clinical condition, which requires the synthesis of knowledge from various disciplines, such as anatomy and biomechanics. Unlike many earlier reviews that focus narrowly on the biological composition or imaging diagnostics of articular cartilage, the present study offers a comprehensive and interdisciplinary perspective that integrates cartilage microstructure, mechanical properties, and both conventional and alternative diagnostic techniques. Particular emphasis is placed on methods capable of assessing the biomechanical and biochemical state of articular cartilage at early stages of degeneration. A distinguishing feature of this review is the critical synthesis of measurement techniques (e.g., indentation, elastography, vibroarthrography) in relation to specific mechanical parameters (e.g., Poisson's ratio, tensile modulus, shear loss angle), which are often discussed in isolation in previous literature.