Osteoarthritis (OA) is a debilitating degenerative joint disease marked by cartilage erosion, synovial inflammation, and hypoxia-driven pain, yet disease-modifying therapies remain elusive. Here, we present a photosynthetic microalgae hydrogel (ALG–TYR/CHL/pEV@DIF) that integrates Chlorella vulgaris–derived oxygen, hydrogen, bioelectricity, and ATP microgeneration with photodynamically active platelet extracellular vesicles loading diferuloylmethane (pEV@DIF) embedded in an alginate–tyramine scaffold. Upon near-infrared (NIR) activation, this living construct simultaneously enhanced O₂/H₂/ATP release, and bioelectric signaling, reprogramming proinflammatory CD86+ M1 macrophages toward reparative CD206+ M2 phenotypes, selectively reducing fibroblast survival while maintaining chondrocyte viability, and reinforcing hydrogel mechanics under compression. In a rat OA model, the hydrogel normalized joint temperature, restored cartilage hydration on T2-weighted MRI with near-healthy signal intensity, and improved stride frequency, reflecting significant pain alleviation. Histological and immunofluorescence analyses further revealed collagen II upregulation, suppressed TNF-α and HIF-1α expression, and systemic biosafety without off-target toxicity. Radiographic and behavioral datasets may provide a useful foundation for future quantitative image and motion analysis, although such approaches were beyond the scope of the present study. Collectively, this photosynthetic microalga hydrogel harnessing photodynamic extracellular vesicles mitigates OA through a minimally invasive, self-powered “green‑gold” strategy for regenerative therapy.