Causes / typical injury mechanism: Osteoarthritis (OA) can be classified as primary or secondary. In primary OA, there is no preceding trauma and the pathogenesis is often multifactorial. Risk factors for primary OA often include genetics, joint morphology, and possibly underlying endocrine abnormalities. Risk factors for secondary OA include fracture, dislocation, and infection. Distal interphalangeal (DIP) joint OA is more common than proximal interphalangeal (PIP) joint OA.

Classic history and presentation: Interphalangeal joints are subjected to high joint reactive forces and experience wear and tear over a lifetime. Patients may experience pain, swelling, stiffness, loss of mobility, and decreased grip strength. It is common for patients with symptomatic interphalangeal joint arthritis to have unremarkable radiographs.

Prevalence: By the age of 85 years, 50% of women and 25% of men will experience hand OA.

Risk factors:

• Modifiable – high body mass index (BMI), occupation
• Nonmodifiable – trauma, age, sex, genetics, race / ethnicity, joint shape

Pathophysiology: The underlying pathophysiology is the loss of articular cartilage, leading to clefts within the cartilage and exposure of bony surfaces. Activation of enzymes and chemical factors that govern cartilage strength and integrity are involved, leading to fractures of superficial cartilage and decreased bone thickness.