Osteoarthritis: Overview and Risk Factors

Osteoarthritis (OA), also known as degenerative joint disease, is the most common joint disorder. It is characterized by hyaline cartilage degeneration and subchondral bone hypertrophy within a joint. Unlike rheumatoid arthritis, OA usually produces minimal inflammation. In severe cases, the articular joint surface may be destroyed, with resultant pain and disability.

OA may be idiopathic or secondary, and multiple factors generally influence its development. Secondary forms are due to endocrine abnormalities (eg, hypothyroid, diabetes mellitus), other joint diseases (rheumatoid arthritis, gout, infection), and bone pathology (avascular necrosis, Paget’s disease).

OA begins with initial articular stiffness, typically lasting less than 15 minutes a day, and gradually progresses to pain with joint motion. The condition often affects weight–bearing joints (knee, hip, or vertebra).

When the hands are involved, the distal interphalangeal (DIP) and the first carpometacarpal (CMC) joints are most commonly affected.

OA rarely affects the elbow, wrist, ankle, shoulder, and temporomandibular joints.

Risk Factors

• Obesity. Knee and hip joints are particularly vulnerable in obese individuals.
• Age. The condition is rare in young people, but common in middle–aged and older adults.¹ One–third of people older than 65 years have radiographic evidence of osteoarthritis in the knee.
• Female gender. Females have adjusted relative risk equal to 2.6, compared with men, although the etiology is uncertain.²
• Occupation. Hands, hips, and knees are vulnerable.
• Genetics. An identical twin of an individual with hand or knee osteoarthritis has double the risk of having the same condition, compared with a fraternal twin.³
• Trauma. Repetitive acts involving any of the vulnerable joints present a cumulative risk.
• Pre–existing or anatomical joint abnormality.
• Poor proprioception and/or quadriceps weakness.
• Knee laxity.