Methods for determining the molecular composition of knee joint structures in osteoarthritis: collagen, proteoglycans and water content: a systematic review

Osteoarthritis is a degenerative disease that affects articular cartilage, leading to changes on the macro and micro levels of this multi-component tissue. Understanding the processes underlying this pathology plays an important role in planning the following management tactics. Timely detection of the knee joint degradation at the level of tissue changes can prevent its progressive damage due to the early beginning of appropriate treatment. This study aimed to provide an overview of the current level of knowledge about the composition of cartilage and menisci using a wide range of different diagnostic methods. A systematic review of the literature published from 1978 to 2023 was conducted. Original studies of the knee joint cartilage (articular and meniscus) research, reporting content composition and mechanical properties, were included. Studies of the non-knee joint cartilage, tissue research other than cartilage and meniscus, or reporting treatment outcomes were excluded (n = 111). Thirty-one papers were included in this review, which reported on the composition of animal and human cartilage (articular and meniscus). The most frequently investigated parameters were quantitative proteoglycan determination and hydration level of the cartilage. Cartilage and meniscus degeneration, i.e., reduced collagen and proteoglycan content, reduced mechanical properties, and increased hydration level, was shown in every article about osteoarthritis. Among all diagnostic methods, laboratory methods (biochemical and histological analysis) are the most frequently used, compared to the instrumental ones (spectroscopy, MRI, and CT). At the same time, spectroscopy takes the lead and becomes the most common approach for determining cartilage composition (collagen and proteoglycans content).

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