Osteoarthritis (OA) was previously thought to be a normal consequence of aging, thereby leading to the term degenerative joint disease. However, it is now realized that OA results from a complex interplay of multiple factors, including joint integrity, genetic predisposition, local inflammation, mechanical forces, and cellular and biochemical processes. (See "Pathogenesis of osteoarthritis".)
The diagnosis of OA is complicated by multiple factors. These include a lack of specific physical or laboratory findings and discrepancies between symptoms and the results of radiographic examinations. As a result, OA is frequently diagnosed by an overall clinical impression based upon the patient's age and history, findings on physical examination, and radiographic findings.
In an attempt to overcome these difficulties, a standardization of the definition, classification, and diagnosis of OA has been attempted using traditional diagnostic criteria and decision trees. These criteria were formulated according to the affected anatomic areas, and include the knee, hand, and hip.
The classification and diagnosis of OA is discussed here, beginning with a review of the different types of OA. The risk factors for and possible causes of OA and the clinical manifestations of this disorder are presented elsewhere. (See "Risk factors for and possible causes of osteoarthritis" and "Clinical manifestations of osteoarthritis".)
TYPES OF OSTEOARTHRITIS
Osteoarthritis (OA) has traditionally been subdivided by etiology into either idiopathic or secondary forms: