Overview of Osteoarthritis

Abstract

Osteoarthritis is the most common type of arthritis thoughout the world. It is among the leading causes of disability and functional loss. Given the aging of the population and the rise in obesity which is a major risk factor for knee and hip osteoarthritis, the prevalence of osteoarthritis is increasing. Painful osteoarthritis of the knee affects at least 12% of persons age 60 and over in the Western World and likely affects an even higher percentage of persons this age in China. While hyaline articular cartilage loss is the signature feature on pathology, the disease affects all structures of the joint in a nonuniform manner, affecting some areas of the joint more than others. Bone remodeling, fibrocartilage (especially meniscal) degeneration, synovitis, and weakness of muscles that bridge the joint all occur at the same time as cartilage loss. While disease begins perhaps with focal cartilage erosion or injury, the joint narrows at the site of erosion, and stress across this region of the joint increases, causing more damage. Misalignment across the joint creates high local stresses which are particularly damaging, pointing to the critical role of mechanical loading in driving the disease process. A vicious cycle of progressive local cartilage loss, bone remodeling, meniscal change, synovitis and misalignment across the joint emerges. Early on in this pathologic sequence, the person has little if any joint pain. Intermittent and mild joint pain starts usually only after considerable joint damage is present. Even after pathology is present, many persons have no joint pain and others develop pain with little evidence of pathology on x-ray. The structures in the joint whose pathology is tied to joint pain include bone and synovium and possibly tears in fibrocartilage or ligaments. Bone marrow lesions on MRI which histologically represent areas of bone damage are probably caused by malalignment related stress. These bone marrow lesions probably cause pain as does synovitis which is present in many osteoarthritic joints. Synovitis can produce fluid which distends the joint capsule which can also cause pain. The course of osteoarthritis is highly variable, but when progression occurs, it is often accompanied by more severe and more consistent joint pain. There are few, if any, effective preventive strategies for osteoarthritis. The main nonsurgical treatments for osteoarthritis are rehabilitative treatments including exercise, strengthening, weight loss, and braces and orthotics. Drug treatments include analgesics and antinflammatory medications. Nutriceuticals and hyaluronans are controversial in terms of efficacy. No treatment has been shown to slow the disease process.