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Pathological Anatomy · Chapter 22. Diseases of the Musculoskeletal System

Osteoarthritis

*Osteoarthrosis*

Osteoarthritis is a common chronic degenerative joint disease. It is based on the progressive destruction and loss of articular cartilage, accompanied by changes in the adjacent bone tissue and periarticular structures.

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Risk of developmentThe incidence increases significantly as the body ages.
Common localizationsHip, knee, cervical, and lumbar spine.
Gender factorThe pathology is diagnosed somewhat more frequently in women than in men.
Primary targetArticular cartilage, which thins, cracks, and fragments.
2 min readFor medical studentsUpdated Sep 25, 2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesReviewed by medical editor: Aulov A. A., general practitioner · 09/24/2026

Causes (Etiology)

The exact causes of the disease are not fully established. Two main forms of the pathology are distinguished depending on the background:

  • Primary (idiopathic) osteoarthritis. It occurs without any apparent causes, typically in elderly individuals.
  • Secondary osteoarthritis. It develops against the background of pre-existing joint changes. Predisposing factors include metabolic disorders, musculoskeletal developmental anomalies, and past injuries.

Mechanisms of development (Pathogenesis)

The pathogenesis of the disease is not fully understood, but the following processes play a key role:

  1. Normal synthesis of proteoglycans and type II collagen is disrupted.
  2. A large amount of hydrolytic enzymes is released, which destroy the matrix.
  3. Remodeling of the extracellular matrix of cartilage tissue and damage to the chondrocytes themselves occur.

Progression of degeneration is promoted by age-related wear of cartilage structures and mechanical overload of weight-bearing joint zones.

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Morphological picture

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

  • Cartilage changes. Chondrocytes die, the tissue thins, fibrillates, and cracks. Detached cartilage fragments enter the joint cavity, forming so-called "joint mice".
  • Bone changes. When cartilage is destroyed, the underlying bone is exposed. Due to friction against the opposing joint surface, osteosclerosis develops in it, and subchondral cysts form.
  • Osteophytes. These are bone growths (spurs) directed outward from the joint space. They traumatize surrounding soft tissues, causing pain syndrome. In the interphalangeal joints of the hands, small osteophytes are called Heberden's nodes.

Clinical manifestations

Symptoms develop gradually. Patients note increasing stiffness in movements, which is especially pronounced in the morning hours. Crepitation (crunching) occurs during movements — the result of friction between exposed bone surfaces. Swelling associated with a chronic inflammatory process in the tissues surrounding the joint is also characteristic.

Briefly: answers to topical questions

What causes primary osteoarthritis?

Primary (idiopathic) osteoarthritis occurs without a visible cause on initially healthy articular cartilage when mechanical loads exceed the norm. The final cause of the disease is unclear, and a single etiological factor has not been identified.

The development of the pathology is caused by the combined effect of biological and mechanical factors:

  • Mechanical overloads — occupational, sports, and domestic loads acting on an unchanged joint.
  • Biological factors — age, genetic (hereditary) predisposition, metabolic disorders, and overweight.
  • Vascular disorders — vascular developmental anomalies.
  • External factors — unfavorable environmental and working conditions.
  • Other factors — concomitant diseases.

Class and exam questions

In which joints does osteoarthritis most frequently develop?

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

What are "joint mice"?

These are free fragments (pieces) of destroyed articular cartilage that enter the joint cavity.

Why does pain occur in osteoarthritis?

Pain is caused by trauma to soft tissues from bone growths (osteophytes), as well as concomitant chronic inflammation of periarticular structures.

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What else to study on this topic

  • Morphology of tophaceous gout and kidney damage in gout
  • Secondary gout: etiology and pathogenesis
  • Congenital dislocation of the hip and hip dysplasia
  • Aseptic osteonecrosis: causes and outcomes
  • Joint tumors (benign and malignant synovioma)
  • Villonodular synovitis and its variants

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Other topics in the section "Chapter 22. Diseases of the Musculoskeletal System"

Bone tissue pathologyOsteomyelitisBone tumorsGoutSkeletal muscle pathologySoft tissue tumorsArthritisPathogenesis and outcomes of diseasesInvasive tumor growthComplications of amyloidosisComplications of osteoporosisComplications of psoriasisComplications and outcomes of atrophy
The entire section "Chapter 22. Diseases of the Musculoskeletal System"

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