Medicine – Risk Factors for Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disorder characterised by progressive loss of articular cartilage, changes in subchondral bone, and varying degrees of synovial inflammation. Although ageing is one of the strongest risk factors, osteoarthritis usually develops through a combination of mechanical stress, genetic susceptibility, previous joint damage, metabolic factors, and abnormalities of joint structure.

1. Increasing Age

Age is one of the most important risk factors for osteoarthritis. With advancing age, articular cartilage becomes less able to repair itself after repeated mechanical stress. Changes in cartilage composition, subchondral bone, muscle strength, and joint mechanics all contribute to the increasing prevalence of OA in older adults.

2. Female Sex

Women have a higher risk of osteoarthritis, particularly after middle age and after menopause. The reason is likely multifactorial and may involve hormonal influences, anatomical differences, and differences in joint biomechanics. Hand and knee osteoarthritis are especially common in women.

3. Genetic Predisposition

A family history and genetic susceptibility can increase the likelihood of developing OA. Genetic factors appear particularly important in osteoarthritis of the hands, hips, and spine. Inherited differences in cartilage structure, bone shape, or connective tissue may make certain joints more vulnerable to degeneration.

4. Obesity

Obesity is a major modifiable risk factor, especially for osteoarthritis of weight-bearing joints such as the knees and hips. Excess body weight increases the mechanical load passing through these joints and accelerates cartilage wear. Adipose tissue may also contribute through metabolic and inflammatory mediators, so the effect is not purely mechanical.

5. Joint Hypermobility

Hypermobility can increase abnormal movement and mechanical stress within a joint. Repeated excessive movement may reduce joint stability and expose articular surfaces to uneven loading, thereby increasing the risk of degenerative change over time.

6. Previous Joint Trauma

A history of significant joint injury is an important cause of secondary osteoarthritis. Fractures that extend through the articular surface are particularly important because they can permanently alter joint congruity and load distribution. Ligament injuries and meniscal damage may also increase later OA risk by producing chronic instability or abnormal biomechanics.

7. Chondrocalcinosis

Chondrocalcinosis, usually related to calcium pyrophosphate deposition, is associated with osteoarthritic change. Crystal deposition can damage cartilage and alter joint mechanics, sometimes producing a pattern of degeneration that differs from typical primary OA.

8. Previous Septic Arthritis

Septic arthritis can cause rapid and severe destruction of articular cartilage. Even after the infection has been successfully treated, residual cartilage damage and joint deformity can predispose the affected joint to secondary osteoarthritis.

Developmental Conditions

9. Congenital or Developmental Hip Abnormalities

Abnormal joint development can produce uneven loading of articular surfaces and markedly increase later OA risk. Developmental dysplasia or congenital dislocation of the hip can alter the relationship between the femoral head and acetabulum, leading to premature degeneration of the hip joint.

Perthes’ disease, in which childhood avascular necrosis affects the femoral head, can also leave residual deformity. The altered shape of the hip may cause abnormal mechanical stress and predispose to osteoarthritis in adult life.

Bone Disorders

10. Paget’s Disease of Bone

Paget’s disease produces abnormal bone remodelling and can change the shape and mechanical alignment of bones near a joint. These structural abnormalities alter the distribution of forces across articular cartilage and may lead to secondary osteoarthritis.

Endocrine and Metabolic Conditions

11. Acromegaly

In acromegaly, excess growth hormone and insulin-like growth factor 1 cause enlargement of bones, cartilage, and soft tissues. These changes alter joint structure and mechanics and may eventually result in a characteristic degenerative arthropathy.

12. Haemochromatosis

Haemochromatosis can produce a characteristic arthropathy through iron deposition and associated metabolic effects on cartilage. It is also strongly associated with calcium pyrophosphate deposition, which can further contribute to joint degeneration.

13. Wilson’s Disease

Wilson’s disease has historically been associated with degenerative joint abnormalities in some patients. Disturbances in copper metabolism may contribute to skeletal and joint changes, although this is a much less common risk factor than age, obesity, prior trauma, or developmental abnormalities.

Key Clinical Concept

The major risk factors for osteoarthritis include increasing age, female sex, genetic predisposition, obesity, hypermobility, and previous joint injury. Secondary OA can also result from conditions that damage cartilage or alter joint anatomy, including septic arthritis, chondrocalcinosis, developmental hip disorders, Paget’s disease, and selected endocrine or metabolic diseases.