Osteoarthritis (OA) is a chronic and progressive degenerative disease that affects joint structures, such as the hips, knees, and hands, involving the articular cartilage, subchondral bone, ligaments, capsule, and synovium. OA is characterized by a progressive degeneration of the joint structures, resulting in pain and decreased quality of life. Local and systemic risk factors pave the way for OA development. Different phenotypes may be identified, but three main molecular mechanisms define the endotypes: the bone-driven endotype, the synovitis-driven endotype, and the cartilage-driven endotype. The hallmark of OA pathophysiology involves more than just mechanical degradation; it includes the release of pro-inflammatory mediators, such as interleukins and TNF-α, which elucidates the significant roles of metabolic syndrome, diabetes, and cellular senescence in its development. OA is distinguished by a clinical presentation that varies significantly between people and is marked by pain, stiffness, and functional impairments. The clinical course can be split into Pre-OA, Early OA, Evident OA, and End-Stage. Depending on the stage of the disease, OA diagnosis frequently necessitates a complex strategy that combines clinical evaluation to detect joint tenderness, range of motion, and joint swelling or abnormalities, medical history assessment, imaging modalities, and laboratory investigations. There is no known treatment for OA, and different therapies are usually evaluated based on the stage of the disease to minimize pain and stiffness while maintaining joint function. Treatments are divided into the reduction of modifiable risk factors, pharmacologic therapies, rehabilitation, complementary therapies, interventional pain procedures, and surgery. OA clinical heterogeneity underlines the importance of prevention, early diagnosis, and identifying the phenotype and endotype to tailor the treatment.