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Osteoarthritis

*Osteoarthrosis*

For medical students2 min readUpdated 2026-10-10

Osteoarthritis is a common chronic degenerative joint disease. It is characterized by the progressive destruction and loss of articular cartilage, accompanied by alterations in the underlying bone and periarticular structures.

Risk of developmentThe incidence increases significantly with advancing age.

Common localizationsHip, knee, cervical, and lumbar spine.

Gender factorThe condition is diagnosed slightly more frequently in women than in men.

Primary targetArticular cartilage, which thins, develops fissures, and fragments.

Causes (Etiology)

The exact causes of the disease are not fully established. Two main forms are distinguished based on the underlying clinical background:

Primary (idiopathic) osteoarthritis. Occurs without any obvious prior cause, typically in elderly individuals.
Secondary osteoarthritis. Develops against the background of preexisting joint abnormalities. Predisposing factors include metabolic disorders, musculoskeletal developmental anomalies, and prior trauma.

Mechanisms of Development (Pathogenesis)

The pathogenesis is not fully elucidated, but the following processes play a key role:

Disruption of normal proteoglycan and type II collagen synthesis.
Release of large amounts of hydrolytic enzymes that degrade the extracellular matrix.
Remodeling of the extracellular matrix of cartilage and damage to chondrocytes themselves.

Progression of the dystrophy is promoted by age-related wear of the cartilaginous structures and mechanical overload of weight-bearing joint zones.

Morphological Features

Changes affect both cartilage and bone, creating the characteristic appearance of deforming osteoarthritis:

Cartilage changes. Chondrocytes undergo apoptosis, and the tissue thins, frays, and develops fissures. Detached cartilage fragments enter the joint cavity, forming so-called «joint mice» (loose bodies).
Bone changes. Cartilage destruction exposes the underlying subchondral bone. Friction against the opposing articular surface leads to osteosclerosis and the formation of subchondral cysts.
Osteophytes. These are bony outgrowths (spurs) extending outward from the joint margin. They traumatize surrounding soft tissues, causing pain. In the interphalangeal joints of the hands, small osteophytes are known as Heberden's nodes.

Clinical Manifestations

Symptoms develop gradually. Patients report progressive joint stiffness, which is especially prominent in the morning hours. Crepitus (crunching or grinding) occurs during movement as a result of friction between exposed bone surfaces. Swelling is also characteristic, associated with a chronic inflammatory process in the tissues surrounding the joint.

Frequently asked questions

What causes primary osteoarthritis?

Primary (idiopathic) osteoarthritis occurs without an apparent cause on initially healthy articular cartilage when mechanical loads exceed normal physiological limits. The definitive cause of the disease is not fully clear, and no single etiologic factor has been identified.

The development of the pathology is driven by the combined effects of biological and mechanical factors:

Mechanical overloads — occupational, athletic, and everyday physical stress acting on a previously normal joint.
Biological factors — age, genetic (hereditary) predisposition, metabolic disorders, and obesity.
Vascular disturbances — vascular developmental anomalies.
External factors — unfavorable environmental and working conditions.
Other factors — comorbid conditions.

Which joints are most commonly affected by osteoarthritis?

The pathology predominantly affects the hip and knee joints, as well as the intervertebral joints of the cervical and lumbar spine. Interphalangeal and other joints are less frequently affected.

What are «joint mice»?

These are free fragments (loose bodies) of destroyed articular cartilage that migrate into the joint cavity.

Why does pain occur in osteoarthritis?

Pain is caused by soft tissue trauma from bony outgrowths (osteophytes), as well as concomitant chronic inflammation of periarticular structures.

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