What is osteoarthritis?

Osteoarthritis is a chronic progressive non-inflammatory disease of the synovial joints of various etiologies, characterized by degeneration of articular cartilage, structural changes in the subchondral bone and overt or latent synovitis.

Until the mid-1980s, there was no unified definition of osteoarthritis. It was usually interpreted as a disease of unknown etiology, in which cartilage is primarily affected (in contrast to rheumatoid arthritis, in which the synovial membrane is primarily affected), and the degenerative nature of the pathological process was indicated.

In 1986, the Osteoarthritis Subcommittee of the American College of Rheumatology (ACR) Committee on Diagnostic and Therapeutic Criteria proposed the following definition of osteoarthritis: "Osteoarthritis is a heterogeneous group of diseases that result in joint symptoms due to deterioration of the articular cartilage and changes in the underlying bone."

The most significant and fully consistent with modern theories of the etiology and pathogenesis of osteoarthritis, as well as most fully reflecting the essence of this disease, is the definition of ACR (1995): “Osteoarthritis is a disease caused by the action of biological and mechanical factors that destabilize the normal relationship between the processes of degradation and synthesis of chondrocytes, the extracellular matrix of articular cartilage and subchondral bone.”

A more extensive but difficult to remember definition, summarizing the clinical, pathophysiological, biochemical and biomechanical changes characteristic of osteoarthritis, was developed at a conference on the etiopathogenesis of osteoarthritis, organized by the National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases, National Institute of Aging, American Academy of Orthopaedic Surgeons, National Arthritis Advisory Board and Arthritis Foundation (Brandt KD et al., 1986): "Clinically, osteoarthritis is characterized by joint pain, tenderness on palpation, limitation of their mobility, crepitus, periodic effusion and local inflammation of varying degrees of severity, but without systemic manifestations. Pathological changes in osteoarthritis are characterized by uneven cartilage loss, more often in areas of increased load, sclerosis of the subchondral bone, formation of subchondral cysts, marginal osteophytes, increased metaphyseal blood flow and inflammation of the synovial membrane. Histologically, early osteoarthritis is characterized by fragmentation of the articular cartilage surface, proliferation of chondrocytes, formation of vertical cracks in the cartilage, deposition of various crystals, remodeling and, possibly, ingrowth of the transitional "wavy" line by blood vessels. Osteoarthritis is also characterized by the presence of signs of a reparative response (in particular, osteophytes); later, total cartilage loss, osteosclerosis and focal osteonecrosis of the subchondral bone occur. Biomechanically, osteoarthritis is characterized by a change in the ability of articular cartilage to resist stretching, compression, changes in its permeability to water, an increase in the concentration of water in it and excessive swelling. Biochemically, osteoarthritis is characterized by a decrease in the concentration of proteoglycans, possibly a change in their size and aggregation, a change in the size and fraying of collagen fibers, and an increase in the synthesis and degradation of matrix macromolecules."

The definition of osteoarthritis proposed at the seminar "New Horizons in Osteoarthritis" (USA, 1994), held by the American Academy of Orthopaedic Surgeons, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institute of Aging, Arthritis Foundation and Orthopaedic Research and Education Foundation, emphasizes that osteoarthritis includes several nosologies: "Osteoarthritis is a group of overlapping diseases that have different etiologies, but the same biological, morphological and clinical outcomes. The pathological process affects not only the articular cartilage, but also spreads to the entire joint, including the subchondral bone, ligaments, capsule, synovial membrane, and periarticular muscles. Ultimately, degeneration of the articular cartilage occurs with its fraying, cracking, ulceration and complete loss."

At a seminar held in 1995, the following definition was proposed: "Osteoarthritis is the result of the action of biological and mechanical factors that disrupt the balance between the processes of degradation and synthesis of the extracellular matrix of articular cartilage and subchondral bone. Osteoarthritis can be initiated by many factors, such as genetic, evolutionary, metabolic and traumatic, and all tissues of the synovial joint are involved in the pathological process in osteoarthritis. Ultimately, osteoarthritis is manifested by morphological, biochemical, molecular and biomechanical changes in cells and matrix that lead to thinning, fissuring, ulceration, loss of articular cartilage, osteosclerosis with a sharp thickening and compaction of the cortical layer of the subchondral bone, osteophytosis, and the formation of subchondral cysts. The clinical picture of osteoarthritis is characterized by arthralgia, pain and limitation of movement, crepitus, periodic accumulation of effusion in the joint cavity, an inflammatory process of varying severity without systemic manifestations."

Historical background of osteoarthritis

According to researchers, people have always suffered from osteoarthritis. Degenerative changes in bones have been found in the fossil remains of Pithecanthropus erectus (Java Man). Similar changes have been found in the bones of the inhabitants of the Nubian cave, who lived 10,000 years BC (Brugsch HG, 1957), as well as in the skeletons of the ancient Anglo-Saxons.

Hippocrates described the disease as "arthritis affecting large joints, which does not extend beyond the affected joint." These clinical observations were subsequently forgotten until the end of the 18th century, when clinicians again attempted to divide arthropathies into groups. Despite the fact that the first detailed and clinically complete description of osteoarthritis was made in 1805 by John Haygarth (a year before William Heberden described nodules in the area of the distal interphalangeal joints), successful attempts to isolate OA as a disease distinct from rheumatoid arthritis were made only at the beginning of the 20th century (Garrod AE, 1907; Hoffa A., Wollenberg GA, 1908; Nichols EH, Richardson FL, 1909). Studying "non-tuberculous" arthritis, E.N. NicholsH FL Richardson (1909) identified two types of changes in the joints: "proliferative type with a tendency to destruction of articular cartilage, which leads to ankylosis" and "degenerative type with a tendency to destruction of articular cartilage without ankylosis". The latter option is obviously a description of osteoarthrosis. Only after the publication of RL Cecil and VN Archer in 1926, the concept of osteoarthrosis as a separate disease was accepted by the general medical community.