Description

• Progressive loss of articular cartilage with reactive changes at joint margins and in subchondral bone
• Primary osteoarthritis (OA)
  • Idiopathic: categorized by clinical features (localized, generalized, erosive)
• Secondary OA
  • Posttraumatic (e.g., ACL rupture, distal radius fracture, shoulder dislocation)
  • Childhood anatomic abnormalities (e.g., congenital hip dysplasia, slipped capital femoral epiphysis [SCFE])
  • Inheritable metabolic disorders (e.g., Wilson disease, alkaptonuria, hemochromatosis)
  • Neuropathic arthropathy (Charcot joints)
  • Endocrinopathies: acromegalic arthropathy, hyperparathyroidism, hypothyroidism
  • Paget disease
  • Noninfectious inflammatory arthritis (e.g., rheumatoid arthritis [RA], spondyloarthropathies)
  • Gout, calcium pyrophosphate deposition disease (pseudogout)
• Synonym(s): osteoarthrosis; degenerative joint disease (DJD)

Epidemiology

• Most common joint disease in United States
• Symptomatic OA most common in patients aged >40 years
• Leading cause of disability in patients aged >65 years
• Predominant sex: male = female
• Predominantly impacts weight-bearing joints

Incidence

• Hip (symptomatic)—88 per 100,000 per year
• Knee (symptomatic)—240 per 100,000 per year

Prevalence

• >30 million patients affected in United States
• Increases with age; radiographic evidence of OA is present in many patients >65 years old.
• 16–20% of patients >65 years old have radiographic evidence of glenohumeral OA.
• Moderate to severe hip OA in 3–6% of whites; <1% in East Indians, blacks, Chinese, and Native Americans

Etiology and Pathophysiology

Failure of chondrocytes to maintain the balance between degradation and synthesis of extracellular collagen matrix. Collagen loss results in alteration of proteoglycan matrix and increased susceptibility to degenerative change.

Genetics

• Up to 65% of OA cases may have a genetic component.
• The heritability of end-stage hip OA is up to 27%.
• >100 polymorphic DNA variants have been associated with OA; these variants account for >20% OA heritability.

Risk Factors

• Increasing age: >50 years
• Age as a risk factor is greatest for hip, knee, and shoulder OA.
• Obesity (weight-bearing joints); BMI >35 kg/m²
• Trauma, infection, or inflammatory arthritis
• Female gender (knee and hand)

General Prevention

Weight management; regular physical activity, peri-joint muscle strengthening (“prehabbing”)

Commonly Associated Conditions

• Obesity
• History of trauma
• Shoulder arthritis can be associated with a rotator cuff tear.