Osteoarthritis (OA) is now widely recognized not merely as a cartilage-centric disease but as a multifactorial disorder affecting the entire joint as an organ, including the articular cartilage, subchondral bone, synovium, ligaments, menisci, and the innervating neural elements. This review explores the complex pathophysiology of OA with a focus on the emerging mechanisms of pain and inflammation that extend beyond articular cartilage degradation. Joint inflammation driven by immune activation in response to cellular stress signals promotes the release of pro-inflammatory mediators and catabolic enzymes. Key signaling pathways such as NF-κB, MAPKs, and JAK/STAT amplify these responses, and pain is sustained through peripheral and central sensitization, contributing to exacerbating symptoms even in the absence of visible joint damage. This review also integrates molecular and cellular mechanisms to highlight innovative therapies aimed at modifying both the structural damage and neurosensory drivers of pain. These approaches offer the potential to not only alleviate symptoms but also alter disease progression, signaling a move toward personalized, mechanism-based treatments. Given the intricate interactions among joint tissues, immune activation, and sensory processing, a comprehensive strategy that targets both structural degeneration and neuroinflammation is essential for the future of OA management. Emphasizing the joint as an integrated organ, we advocate for translational research linking molecular pathology with clinically meaningful outcomes.

Intervertebral disc (IVD) disease is typically characterized by the degradation of IVD tissue, secretion of inflammatory and painful factors, and hyperinnervation of the disc. The pro-inflammatory cytokine interleukin-1β (IL-1β) has been regarded as a principal factor in orchestrating disc degeneration. Link N (LN) is a peptide derived from the link protein that has been shown to promote extracellular disc regeneration even in an inflammatory milieu; however, no mechanism(s) has been described for their behaviour to date. Building on prior studies on LN, we hypothesize that LN directly inhibits IL-1β. IVD degeneration was experimentally induced in New Zealand white rabbits, followed by the injection of either sLN or saline as the vehicle control. To determine the expression of markers of pain, histology was performed. Cultured human Nucleus Pulposus disc cells (hNP) were used to determine the effects of LN on IL-1β-induced changes in gene expression, including the effects on IL-1β, TNFα, and IL6 signalling. Isolated murine dorsal root ganglia (DRG) neurons were used to assess the effect of LN on IL-1β-induced neuronal hyperactivity. LN significantly reduced IL-1β-induced NF-κB activation in a dose-dependent manner in disc cells and was further able to modulate IL-1β-induced gene expression, inflammatory mediators, and neurotrophic factors. Peptide docking simulations revealed that LN could interact with IL-1β. A direct interaction of LN and IL-1β was revealed through co-immunoprecipitation experiments. Although IL-1β was able to hypersensitize DRG neurons following a seven-day exposure, as demonstrated by Ca²⁺ imaging, this effect was significantly blunted when co-treated with LN. LN demonstrates a novel mechanism of action by directly inhibiting IL-1β, in addition to mitigating IL-1β-induced hypersensitivity in DRG neurons. These data suggest a potential role for LN in reducing discogenic pain.

Articular cartilage has a limited capacity for self-repair due to its avascular nature, dense extracellular matrix, and low cellularity. Current treatments for cartilage injury and osteoarthritis (OA) often provide temporary symptom relief but do not restore native tissue structure or function. Intra-articular (IA) administration enables localized delivery of therapeutic agents; however, its effectiveness is limited by rapid clearance from the joint, poor cartilage penetration, and insufficient tissue retention. Controlled-release systems, including scaffolds, hydrogels, nanoparticles, and stimuli-responsive platforms, have been developed to address these barriers by prolonging local therapeutic exposure and enabling sustained or targeted delivery. Preclinical studies have demonstrated the potential of these systems to reduce inflammation and support cartilage protection and repair. However, clinical evidence remains limited, and further studies are required to determine whether these delivery advantages translate into sustained disease-modifying or regenerative outcomes in patients. This review discusses the biological barriers that limit effective IA delivery and summarizes recent advances in controlled-release strategies, with particular attention to their ability to improve joint retention, cartilage penetration, and sustained therapeutic exposure. The advantages and limitations of the different delivery platforms are critically discussed, together with the translational challenges that currently limit their progression from preclinical studies to clinical application.