Nanotherapeutic Strategies for Osteoarthritis: Targeting Aging, Metabolism and Inflammation.

Osteoarthritis (OA) is no longer viewed as a mere "wear-and-tear" disease, but rather as a multifactorial joint failure syndrome driven by cellular senescence, metabolic dysregulation, and low-grade chronic inflammation. These pathological pillars synergistically disrupt cartilage homeostasis, subchondral bone remodeling, and synovial inflammation, collectively fueling disease progression. While conventional therapies offer only symptomatic relief, they fail to reverse or reprogram the underlying pathological microenvironment. Consequently, there is an urgent need to develop disease-modifying interventions that can simultaneously target these pathological pillars. Here, we critically examine how nanomaterial-based platforms-leveraging tailorable surface chemistry, cartilage-penetrating dimensions, and stimuli-responsive cargo release-enable precision targeting of these interconnected mechanisms. We highlight advances in senolytic delivery for senescent cell clearance, redox-modulating nanozymes for metabolic reprogramming, and immunoregulatory strategies for macrophage repolarization, emphasizing designs that transcend passive drug delivery to actively remodel the joint microenvironment. By integrating mechanistic insights with engineering innovation, this review outlines a roadmap for next-generation disease-modifying nanomedicines that promise not merely to slow OA progression, but to restore the biological clock of the joint. We also discuss current translational barriers and propose future directions for personalized OA therapy.