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.

In wrist OA, primary OA is caused by avascular necrosis or congenital deformities and commonly involves the scaphotrapeziotrapezoid (STT) joint. Secondary OA is generally brought about by trauma, particularly scapholunate ligament injury, distal radius fracture, and scaphoid fracture. The majority of cases of wrist arthritis are a result of scapholunate advanced collapse (SLAC).

Wrist OA from 3 types of insult:

1. Ligament injuries –
   • Scapholunate ligament injury leading to SLAC wrist
   • Lunotriquetral injuries
   • Triangular fibrocartilage complex (TFCC) injuries and degeneration
2. Fractures –
   • Chondral lesions following carpal bone fractures
   • Distal radius fracture, distal ulna fracture
   • Scaphoid fractures with nonunion leading to scaphoid nonunion collapse (SNAC) wrist
3. Vascular supply –
   • Preiser disease: avascular necrosis of scaphoid bone (often from trauma)
   • Kienböck disease: avascular necrosis of lunate bone (often from trauma)

Classic history and presentation: Patients will typically present with pain, swelling, stiffness, loss of mobility, and decreased strength.

Prevalence: The prevalence of wrist OA varies within the literature; however, one study found that 1.7% of men and 1.0% of women have wrist OA confirmed radiographically.

Risk factors:

• Modifiable: high body mass index (BMI), occupation
• Nonmodifiable: trauma, advanced age, genetics, joint shape

Pathophysiology: The underlying pathophysiology is the loss of articular cartilage, which leads 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.