Osteoarthritis is the most common joint disease, affecting over 60 % of the elderly population, leading to incapacity of movement. The primary form is usually oligoarticular. In case of an underlying systemic disease or local injury, the cartilage destruction is considered as secondary osteoarthritis. The pathogenesis of primary osteoarthritis suggests an intrinsic disease of cartilage in which biochemical and metabolic alterations result in its breakdown. Within the last decades, different models were established concentrating on joint structures such as bones or ligaments. Changes of the subchondral bone were found to precede cartilage damage, suggesting a primary alteration of the subchondral region. Other studies concentrated on the metabolic activity of chondrocytes in healthy cartilage of patients with osteoarthritis. The precise event that leads to these changes is still not clear. This review concentrates on the histological features in the course of the disease and provides a summary on different pathogenetic risk factors.