Among available papers published on the given subject over the last century, various terms have been used as synonyms for one, now generally accepted—osteoarthritis, in some countries called “wear and tear” or “overload arthritis”. The opsolent terms—hypertrophic arthritis, degenerative arthritis, arthritis deformans and osteoarthrosis—sought to highlight the dominant clinical signs of this ubiquitous, polymorph disease of the whole osteochondral unit, which by incidence and prevalence represents one of the leading chronic conditions that cause long-term pain and incapacity for work. Numerous in vitro and in vivo research resulted in broadened acknowledgments about osteoarthritis pathophysiology and pathology on both histological and cellular levels. However, the cause of osteoarthritis is still unknown and is currently the subject of a hypothesis. In this paper, we provide a review of recent findings on biological phenomena taking place in bone tissue during osteoarthritis to the extent useful for clinical practice. Choosing a proper radiological approach is a conditio sine qua non to the early diagnosis of this entity.

Subchondral bone tissue plays a key role in the initiation and progression of human and experimental osteoarthritis and has received considerable interest as a treatment target. Elevated bone turnover and remodeling leads to subchondral bone sclerosis that is characterized by an increase in bone material that is less mineralized. The aim of this study was to investigate whether perturbations in subchondral bone-resident progenitor cells might play a role in aberrant bone formation in osteoarthritis. Colony formation assays indicated similar clonogenicity of progenitor cells from non-sclerotic and sclerotic subchondral trabecular bone tissues of osteoarthritic knee and hip joints compared with controls from iliac crest bone. However, the osteogenic potential at the clonal level was approximately two-fold higher in osteoarthritis than controls. An osteogenic differentiation assay indicated an efficient induction of alkaline phosphatase activity but blunted in vitro matrix mineralization irrespective of the presence of sclerosis. Micro-computed tomography and histology demonstrated the formation of de novo calcified tissues by osteoblast-like cells in an ectopic implantation model. The expression of bone sialoprotein, a marker for osteoblast maturation and mineralization, was significantly less in sclerotic progenitor cells. Perturbation of resident progenitor cell function is associated with subchondral bone sclerosis and may be a treatment target for osteoarthritis.

The increasing interest in biologic treatments for musculoskeletal disorders has led to the advancement of orthobiologics, particularly in non‐operative care through injectable therapies. However, defining these treatments clearly is crucial for proper clinical application. Orthobiologics include biologic substances that enhance healing, such as cell‐based therapies and blood‐derived products. Among these, platelet‐rich plasma (PRP) is widely used, but its classification remains complex due to variations in preparation methods, platelet concentration, leucocyte content, and activation techniques. Strictly, the term ‘PRP’ refers to plasma enriched in platelets relative to baseline blood levels. Yet, scientific debate persists regarding whether platelet count or enrichment is more significant in clinical outcomes. Additionally, leucocyte‐rich and leucocyte‐poor PRPs offer different therapeutic advantages depending on the target tissue, complicating standardization. Similarly, the presence of red blood cells is generally discouraged, given their association with joint inflammation. Beyond the classical ‘PRP’ formulations, alternative blood‐derived products offer distinct biological effects. A standardized classification system is therefore essential for research and clinical application, emphasizing precise documentation of products' characteristics, including platelet count, activation state and bioactive molecule interactions. Understanding these variables and their impact on patient‐specific conditions will refine orthopaedic regenerative strategies and optimize treatment efficacy.