The pathogenesis of osteoarthritis is not precisely known. Considering its multifactorial nature, each individual case may represent a unique combination of factors. Yet beneath this heterogeneity, it is thought that the origin of osteoarthritis may be related to either abnormal mechanics or biologic failure, or a combination of the two.
Biologic failure describes an inability of the cellular capacity to respond to joint stress.
Abnormal mechanics describes failure of the cartilage related to excessive load bearing across a joint. The degree of load bearing across articular cartilage is proportional to the contact area between the two bones. Loss of this surface area, through medial menisectomy in the knee or acetabular dysplasia in the hip, can significantly increase the unit loading to the articular cartilage. Loosening of the collagen network and increased water content of the cartilage are thought to be the earliest pathologic changes. Much research has been focused on the role of occupation and repetitive motion on the development of osteoarthritis.